Glory (1391)  (doxa from dokeo = to think) means to give a proper opinion or estimate of something and thus the glory of God expresses all that He is in His Being and in His nature, character, power and acts. Doxa is used repeatedly in the Greek Septuagint (LXX) to describe the (Shekinah) glory of God.

For example at Mt Sinai

Nature (5287) (hupostasis [word study] from hupo = under + histemi = stand, referring to a foundation, ground on which something is built)  is literally that which stands under anything (e.g., the foundation of a building). Hupostasis is setting under and thus describes a support, a confidence, a steadiness, a foundation (refers to ground on which something is built = e.g., the foundation of things for which we hope in Heb 11:1 [note]). 

Stated another way hupostasis is that which underlies the apparent and which therefore is the reality, the essence or the substance. It came to denote essence, substance or the inner nature and as discussed below is used with that meaning in here in Hebrews 1:3.  The author is conveying the truth that whatever the divine essence is, Jesus is said to be its perfect expression and in so doing affirms the deity of Jesus Christ. The etymological equivalent of hupostasis in English is substance  or that which stands under a thing and which makes it what it is. The Son is such a revelation of the Father that when we see Jesus, we see what God's real being is.

Hupostasis is a very common word from Aristotle on and was used in Greek to describe that which stands under anything such as a building, a contract, a promise. It is common in the papyri in business documents as the basis or guarantee of transactions or with the meaning of a title deed.

Hupostasis is used 19 times in the Septuagint (LXX) and 5 times in the NT...

2Cor 9:4 (3 But I have sent the brethren, that our boasting about you may not be made empty in this case, that, as I was saying, you may be prepared) 4 lest if any Macedonians come with me and find you unprepared, we (not to speak of you) should be put to shame by this confidence.

2Cor 11:17 That which I am speaking, I am not speaking as the Lord would, but as in foolishness, in this confidence of boasting.

Hebrews 1:3 And He is the radiance of His glory and the exact representation of His nature (hupostasis,  and upholds all things by the word of His power. When He had made purification of sins, He sat down at the right hand of the Majesty on high;

Hebrews 3:14 For we have become partakers of Christ, if we hold fast the beginning of our assurance firm until the end;

Hebrews 11:1 Now faith is the assurance of things hoped for, the conviction of things not seen.

Considering these meanings of hupostasis in Hebrews 11:1 one could paraphrase this verse as follows...

Faith is the title-deed of things hoped for.

Faith is the foundation, the quality of confidence which leads one to stand under, endure, or undertake anything.

Faith involves the most solid possible conviction, the God-given present assurance of a future reality.

Robertson commenting on the use of hupostasis in Hebrews 1:3  writes that...

The word hupostasis for the being or essence of God “is a philosophical rather than a religious term” (Moffatt). Etymologically it is the sediment or foundation under a building (for instance). In  Hebrews 11:1 hupostasis is like the “title-deed” idea found in the papyri. Athanasius rightly used Heb 1:1-4 in his controversy with Arius. (Robertson, A. Word Pictures in the New Testament)

Wuest writes that...

Vincent commenting on hupostasis in Hebrews 1:3 notes that...

The primary sense of hupostasis or substance is something which stands underneath; foundation, ground of hope or confidence, and so, assurance itself. In a philosophical sense, substantial nature; the real nature of anything which underlies and supports its outward form and properties. In N. T., 2Cor. 9:4; 11:17; Heb 3:14; 11:1, signifying in every instance ground of confidence or confidence.

In LXX, it represents fifteen different words, and, in some cases, it is hard to understand its meaning, notably 1Sa 13:21. In Ruth 1:12 ("Return, my daughters! Go, for I am too old to have a husband. If I said I have hope, if I should even have a husband tonight and also bear sons"); Ps. 39:7 ("And now, Lord, for what do I wait? My hope [my ground, my foundation...for hope] is in Thee."); Ezek. 19:5, it means ground of hope: in Jdg. 6:4 ("So they would camp against them and destroy the produce of the earth as far as Gaza, and leave no sustenance [Lxx - hupostasis + zoe ~ no support or foundation of life] in Israel as well as no sheep, ox, or donkey."); Wisd. 16:21, sustenance: in Ps. 39:5 ("Behold, Thou hast made my days as handbreadths, And my lifetime [Lxx = hupostasis ~ my existence] as nothing in Thy sight, Surely every man at his best is a mere breath. Selah."); Ps 139:15, the substance or material of the human frame: in 1Sa 13:23 ("and the garrison of the Philistines"); Ezek. 26:11, an outpost or garrison: in Deut. 11:6; Job 22:20 ("and their abundance the fire has consumed"), possessions.

The theological sense, person, is later than the apostolic age. In Hebrews 1:3, substantial nature, essence. (Adapted and amplified from Vincent, M. R. Word Studies in the New Testament 4:382-383)

In summary, the radiance of His glory speaks of Jesus' oneness or identity with God the Father whereas the exact representation of His nature speaks of Jesus' distinctness and thus of the plurality of the Godhead.

Vine adds that the essence of this phrase is to explain that

the Son of God is a distinct Person from the Father and yet One with Him in the Godhead. He is His equal, as being the perfect representation of His essence.

AND UPHOLDS ALL THINGS BY THE WORD OF HIS POWER: pherôn (PAP) te ta panta tôi rhêmati tês dunameôs autou: (Ps 75:3; Jn 1:4; Col 1:17; Rev 4:11) (Eccl 8:4; Ro 1:16; 2Cor 4:7)

bearing up also the all things by the saying of his might (YLT)

sustaining all the [things] by the word of His power (ALT)

supporting all things by the word of his power (BBE)

He holds everything together with his powerful word (ICB)

sustaining, guiding, and propelling all things by the word of His power (Wuest)

He regulates the universe by the mighty power of his command (TLB)

He sustains the universe by the mighty power of His command (NLT)

He holds everything together through his powerful words (GWT)

upholding and maintaining and guiding and propelling the universe by His mighty word of power (Amp)

sustains the universe with His word of power (Moffatt)

bearing up all things by the utterance of His power (Rotherham)

the utterance of Divine power (Pulpit Commentary)

Upholds (5342)  (phero) means to bear or carry and wa s used to describe a ship being carried along, borne or driven along by the wind (Acts 27:15) or of the men who wrote Scripture as being "moved by the Holy Spirit" (2Pe 1:21-note).

An illustration of this use of phero is found in the Septuagint (LXX)  where Moses says,

I alone am not able to carry (phero) all this people, because it is too burdensome for me,” (Nu 11:14) (Comment: Here phero has in it the idea of the responsibility of the government and guidance of Israel)

The author does not see Christ's work in sustaining creation as if He were an "Atlas-like" figure holding up the universe as a dead weight and otherwise doing nothing. To the contrary upholds indicates that He is carrying it along, bearing it toward its final consummation. The picture is that of continuous (present tense) active and dynamic involvement by the Creator with His creation, not a passive and static (deistic) involvement. The Lord Jesus holds all things together and in their proper relationship to each other by His own power. The oceans are held in their beds. The rivers run down into the sea. The heavenly bodies are held in their orbits.

Vincent says that this phrase

is concerned, not only with sustaining the weight of the universe, but also with maintaining its coherence and carrying on its development..." and adds that "the Logos is called by Philo the bond of the universe; but the maintenance of the coherence implies the guidance and propulsion of all the parts to a definite end."

The Psalmist quotes God as saying

It is I Who have firmly set (the earth's) pillars. Selah." (Ps 75:3).

Paul adds that Jesus

"is before all things and in Him all things hold together." (Col 1:17-note)

The things created by Christ are now being sustained, or conserved, or held together by Him. 

In Him we live, and move, and have our being (exist)" (Acts 17:28). 

By Him all things were created in the past, by Him all things consist in the present and by Him all things are to be reconciled in the future

for from Him and through Him and to Him are all things. To Him be the glory forever. Amen." (Ro 11:36-note)

All things (3956) (pas) refers to the totality, the universe considered as one whole. Nothing is excluded from the scope of the Son's sustaining, supporting, upholding activity. The author pictures the Son as not only active in creation but then as bearing the all time and space towards the fulfillment of the divine plan.

What an awesome truth that the whole universe hangs on the word of Christ for its moment by moment existence! How this flies in the face of the modern teaching on self-sufficiency. We must see that Christ upholds all things by the word of His power and that all things includes the preservation of even our very spirit, soul and body. Our daily existence depends solely upon the word of Christ's power! Therefore as the writer of proverbs exhorts us:

Trust in the LORD with all your heart, and do not lean on your own understanding. In all your ways acknowledge Him, and He will make your paths straight" (Pr 3:5, 3:6)

Why? Because He upholds all things by the Word of His power.

Worship Him today for Who He is, God Himself, and for the profound truth that the Word of His power preserves and assures our very existence.

The word of His power -- In other words Christ's spoken word is that by which the Son's power is manifest (click for one manifestation of this power!). And remember beloved, this is the same "word" He speaks to those who are "His own possession". What has He spoken to you this week in and through His Word? O how we need to remember that it is not just any word but is the word of His power, the very word by which His omnipotent power is manifest in and through our life! "He who has an ear, let him hear what the Spirit" of Christ would say to us today!

Word (4487) (rhema [word study] from verb rheo = to speak - to say, speak or utter definite words) refers to the spoken word, especially a word as uttered by a living voice. Laleo is another word translated speak but it refers only to uttering a sound whereas rheo refers to uttering a definite intelligible word. Rhema refers to any sound produced by the voice which has a definite meaning. It focuses upon the content of the communication. For example in Luke we read...

Rhema as used here in Hebrews 1:3 to refer to active and powerful word. r Rhema is the same word that spoke all that did not exist into existence...

By faith we understand that the worlds were prepared by the word (rhema) of God, so that what is seen was not made out of things which are visible. (see note Hebrews 11:3).  

God the Son spoke and created but He still speaks and sustains. As we listen and obey what God says in His Son (in His Word, the Scripture), He will sustain us through any trial, bringing us to the desired end He has for us --to be conformed to the image of Jesus Christ.  The "word" is not empty. It has force. It does things.

Power (1411) (dunamis from dunamai = to be able) refers to inherent power residing in something by virtue of its nature. Click word study of dunamis.

Luke gives us a correct sense of the power of God's word declaring that 

No (absolute negation) word (rhema - spoken word) from God shall be void of power. " (Lk 1:37ASV, Lk 1:37KJV)

An illustration of this principle is found in Romans where Paul explains that

the gospel...is the power (dunamis) of God for salvation to everyone who believes, to the Jew first and also to the Greek." (Ro 1:16-note)

Thus the Son's Word, the Word of God, is unlike any other word for it has an inherent power because it is God speaking. Are you listening?

Jesus sustains all things by His Word, and that Word has a divine power. The various parts of the physical universe are not held together and regulated merely by laws of nature but these very laws are His laws, and operate by His decree. He can interfere with them at any time, and will do so in the way appointed by Him. Are you trusting in the word of His power to uphold you in whatever difficult circumstance or affliction you are currently experiencing?

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WHEN HE HAD MADE PURIFICATION OF SINS: poiesamenos (AMPMSN) katharismon tôn hamartiôn: (Heb 7:27; 9:12; 13, 14, 16, 26, Jn 1:29; 1Jn 1:7; 3:5)

through himself having made a cleansing of our sins (YLT)

when He had by Himself purged our sins (KJV)

having given Himself as an offering making clean from sins (BBE)

The Son made people clean from their sins (ICB)

effected in person the reconciliation between God and man (Phillips)

He is the one who died to cleanse us and clear our record of all sin (TLB)

After he died to cleanse us from the stain of sin (NLT),

After achieving forgiveness for human sins (TEV)

When He had by offering Himself accomplished our cleansing of sins and riddance of guilt (Amp)

As Matthew Henry so eloquently puts it

From the glory of the person of Christ he proceeds to mention the glory of his grace.

Had made (4160) (poieo) can be translated make, produce, bring about or cause, referring to any external act as manifested in the production of something tangible or obvious to the senses. Poieo is aorist tense which indicates a once-for-all-time, past completed and effective action (cf Christ's triumphant cry from the Cross "It is finished" Jn 19:30).

The author amplifies on this truth writing that Jesus functioned as both the Sacrifice (Offering) and the Sacrificer ("Offerer" or High Priest), Who

"does not need daily, like those high priests (Levitical priests under the Old Covenant), to offer up sacrifices, first for His own sins, and then for the sins of the people, because this He did once for all when He offered up Himself." (see notes Hebrews 7:27;  9:25; 9:26)

Poieo is in the middle voice which signifies that the subject either acts upon himself or in his own interest and thus it conveys a reflexive sense (often translated by adding the reflexive English pronoun "himself").

The phrase can thus be translated He Himself had made indicating that when the Son of God made purification of sins, He did so by Himself, acting upon Himself, offering Himself as the Sacrifice for sin (Heb 9:26-note; He 10:12-note), and for Himself, acting in His own interest. To say it another way the work of purification was done by Christ personally, and was not something which He designated to be done by some other agent. The author emphasizes this truth later writing that "now once at the consummation of the ages He has been manifested to put away sin by the sacrifice of Himself." (He 9:26-note  cf other uses in Hebrews of this key idea of  "Himself" = Heb 2:14, 9:14, 9:25, 26- see notes He 2:14, 9:14; 9:25; 26)

Vincent notes that

In carrying on all things toward their destined end of conformity to the divine archetype, the Son must confront and deal with the fact of sin, which had thrown the world into disorder, and drawn it out of God’s order. In the thought of making purification of sins is already foreshadowed the work of Christ as High Priest, which plays so prominent a part in the epistle."

Purification (2512)  (katharismos from katharizo = to cleanse and our English word catharsis which Webster's defines as purification or purgation that brings about spiritual renewal or release from tension) describes the process of making clean, cleansing, purifying, freeing from filth. Although the cleansing could refer to cleansing from physical stain or contamination, by far the most important aspect is cleansing from the "stain" of sin. This picture and the use of this word katharismos would not be lost on the Jewish readers, all of whom would be very familiar with the cleansing ritual on the Day of Atonement as described in Leviticus 16 (Lev 16:29) which concludes with the statement that

on this day that atonement shall be made for you to cleanse (or purify) (LXX uses katharizo the root of katharismos) you You shall be clean (LXX = katharizo ) from all your sins before the LORD. (Lev 16:30)

Katharismos - 7x in 7v - Mark 1:44; Luke 2:22; 5:14; John 2:6; 3:25; Heb 1:3; 2 Pet 1:9. NAS = cleansing(2), purification(5).

Sins (266)  brought death to man and separation from fellowship and communion with God. Sinful man needed purification of sins which in the Old Testament system required  a priest to carry out the purification ritual. Thus the author adroitly introduces the idea of  the Son, Christ Jesus, as the High Priest Who effects purification of sins by offering up the Sacrifice of His body on the Cross as a payment for man's sin. In the Old Testament the priests had to make sacrifices day after day and year after year not only for the purification of the people but also for themselves. Jesus made but one sacrifice when He offered Himself and because His sacrifice is unblemished and spotless (1Pe 1:18, 19-notes), He can purify our sins, something that all the Old Testament sacrifices together could never accomplish

The writer of Hebrews goes to great lengths to explain Christ's sacrificial role and how His sacrifice made the Old Covenant sacrifices obsolete...

For it is impossible for the blood of bulls and goats to take away sins" (He 10:4-note), "but when Christ appeared as a High Priest...He entered through the greater and more perfect tabernacle (in contrast to the earthly tabernacle and the Holy of holies that the Levitical priests entered once a year on the Day of Atonement) and not through the blood of goats and calves, but through His own blood... (into) the holy place once for all, having obtained eternal redemption. For if the blood of goats and bulls and the ashes of a heifer sprinkling those who have been defiled, sanctify for the cleansing of the flesh, how much more will the blood of Christ, who through the eternal Spirit offered Himself without blemish to God, cleanse (or "purify" - katharizo) your conscience from dead works to serve the living God? … but now once at the consummation of the ages He has been manifested to put away sin by the sacrifice of Himself." (see notes Hebrews 9:12;  9:13; 9:14;  9:26).

MacArthur notes that

This truth must have seemed especially remarkable to those to whom the book of Hebrews was first written. The cross was a stumbling block to Jews, but the writer does not apologize for it. Instead, he shows it to be one of the seven excellent glories of Christ. (MacArthur, John: Hebrews. Moody Press or Logos)

MacDonald nicely summarizes the purifying work of the Son writing that

he Creator and the Sustainer became the Sin-bearer. In order to create the universe, He only had to speak. In order to maintain and guide the universe, He only has to speak...but in order to put away our sin once for all, He had to die on the cross of Calvary. It is staggering to think that the sovereign Lord would stoop to become the sacrificial Lamb. “Love so amazing, so divine, demands my soul, my life, my all,” as Isaac Watts’ hymn says." (MacDonald, W & Farstad, A. Believer's Bible Commentary: Thomas Nelson  or Logos)

HE SAT DOWN AT THE RIGHT HAND OF THE MAJESTY ON HIGH: ekathisen (3SAAI) en dexia tes megalosunes en hupselois: (Hebrews 4:14; 8:1; 10:12; 12:2; Ps 110:1; Mk 16:19; Lk 20:42;43 Acts 2:33; 7:56; Ro 8:34; Ep 1:20;21, 22, Col 3:1; 1Pe1:21; 3:22; Rev 3:21) (Majesty 1Chr 29:11; Job 37:22; Mic 5:4; 2Pe 1:16; Jude 1:25)

sat down at the right hand of the greatness in the highest (YLT)

Then he sat down at the right side of God, the Great One in heaven (ICB)

then sat down in highest honor beside the great God of heaven (TLB)

He sat down in the place of honor at the right hand of the majestic God of heaven. (NLT)

He received the highest position, the one next to the Father in heaven (GWT)

He sat down in heaven at the right-hand side of God, the Supreme Power (TEV)

Matthew Henry again puts it eloquently writing that

From the glory of his sufferings we are at length led to consider the glory of his exaltation...Having assumed our nature, and suffered in it on earth, He has taken it up with Him to heaven, and there it has the high honor to be next to God, and this was the reward of His humiliation.

He sat down (2523) (kathizo) represents a  a formal and dignified act and is a reference is to the Son’s glorification and ascension and His regal position as King.  The Son seated at the right hand is never used of Christ's pre-existing state co-equal with the Father, but always of His exalted state as Son of man after His sufferings. Now as our Mediator He "intercedes for us" in the presence of God. (see note Romans 8:34).

Hughes remarks that this

"thought is utterly sublime but true—this glorious Cosmic Being at the apex of His splendor is praying for you and me! Can it really be? Yes! God’s Word says it is so. Wonder of wonders!"  (Hughes, R. K. Hebrews: An Anchor for the Soul. Volume 1.  Crossway Books; Volume 2 or Logos)

Vine adds that

"this position was a ratification of the perfect fulfillment of all that He had accomplished in His expiatory (making atonement) sacrifice for sins." (Vine, W. Collected writings of W. E. Vine. Nashville: Thomas Nelson or Logos

The seated posture is one of of rest and yet in His exalted state Jesus is still bearing on all things toward their destined consummation, and is still dealing with sin as the Great High Priest, saving believing sinners in His precious blood and cleansing saints from the daily defilement of sin. This is not the rest following toil, but the rest of satisfaction in a finished work (cf "once for all" or "for all time" in the following verses - Heb 7:27-note; He 9:12-note, He 10:10-note, He 10:12-note; He 10:14-note John 19:30)

This posture indicates that the work of redemption has been completed. The seated posture of the High Priest Jesus Christ is in contrast to the Levitical priests who never sat down so far as their tabernacle work was concerned because their work was never finished, because

the Law, since it has only a shadow of the good things to come and not the very form of things, can never by the same sacrifices year by year, which they offer continually, make perfect those who draw near" (see note Hebrews 10:1) 

Why? Because

it is impossible for the blood of bulls and goats to take away sins." (see note Hebrews 10:4)

In the OT David prophesies and quotes the Father inviting the Son to

Sit at My right hand until I make Thy enemies a footstool for Thy feet."  (Ps 110:1)

While on earth our Lord applied the Psalm to Himself stating that 

 from now on THE SON OF MAN WILL BE SEATED AT THE RIGHT HAND of the power OF GOD.” (Lk 22:69).

We see the fulfillment in Hebrews where the author says that

"the main point in what has been said is this: we have such a high priest, who has taken His seat at the right hand of the throne of the Majesty in the heavens" (see notes Hebrews 8:1; Hebrews 10:12; Hebrews 12:2)

Paul explains the significance of Jesus' present Kingly and Priestly position writing that God

raised Him from the dead, and seated Him at His right hand in the heavenly places, far above all rule and authority and power and dominion, and every name that is named, not only in this age, but also in the one to come. And He put all things in subjection under His feet, and gave Him as head over all things to the church" (see notes Ephesians 1:20; 1:21; 1:22) 

Peter adds that Jesus is

at the right hand of God, having gone into heaven, after angels and authorities and powers had been subjected to Him." (see note 1 Peter 3:22)

Luke tells us that after Jesus had

"been exalted to the right hand of God, and (had) received from the Father the promise of the Holy Spirit, He has poured forth this which you both see and hear (the Spirit at Pentecost)" (Acts 2:33)

Finally John offers this encouragement to all believers quoting Jesus Who is presently seated

"at the right hand of the majesty on high" promising that to Him "who overcomes, I will grant to him to sit down with Me on My throne, as I also overcame and sat down with My Father on His throne." (see note Revelation 3:21)

And in one of the most incredible invitation every given, we as believers have been given the awesome invitation to

"draw near with confidence to the throne of grace, that we may receive mercy and may find grace to help in time of need." (see note Hebrews 4:16)

Do you need grace to make it today? I do. Let us draw near with holy boldness.

Majesty (3172)  (megalosune from mégas = great, strong)  refers to a state of greatness, importance, prominence and specifically as here is a title for God Who is characterized by majesty and greatness. The use of Majesty as a title for God may be rendered in some languages as `the one who is truly great' or ` truly important.'

Right (1188)  (dexios) as opposed to left and when giving or receiving, preference is given to right hand (Christ is God's literal "Right hand Man") and so the right-hand position is the place of honor. It was the custom of ancient kings in the East to place at their right hand the son whom they associated with themselves in the prerogatives of royalty. It is also a place of delight for the psalmist says

In Thy right hand there are pleasures forever." (Ps 16:11-note).

Clearly this is also the position of privilege for the author of Hebrews asks in this same chapter

"which of the angels has He ever said, "SIT AT MY RIGHT HAND, UNTIL I MAKE THINE ENEMIES A FOOTSTOOL FOR THY FEET"? (see note Hebrews 1:13) 

This Old Testament quotation in the preceding verse is from Ps110:1 which reads

(A Psalm of David.) The LORD (Jehovah) says to my Lord (Adonai): "Sit at My right hand, Until I make Thine enemies a footstool for Thy feet.

Jesus taking His seat at the right hand of God is taken from Ps 110:1-note where David writes...

The LORD (God the Father) says to my Lord (God the Son): "Sit at My right hand, until I make Thine enemies a footstool for Thy feet." (Comment: Literally this begins "Jehovah said to Adonai". David records a remarkable conversation between two Persons of the Godhead. This Messianic psalm is quoted as such at least 12 times in the NT. In Mt 22:43, 44, 45 Christ specifically applies Psalm 110:1 to Himself claiming that He is not just the son of David but David's Lord. In short, Psalm 110 pictures the Messiah as King, Priest and victorious Warrior.

Psalm 110:1 is quoted 5 times in the NT -- Mk 12:36,  Lk 20:42; Acts 2:34, Heb 1:13 and Heb 10:12. There are 15 other Scriptural references to Christ seated at the right hand of God:

Ps 16:11 [KJV "at Thy right hand"], Mt 26:64; Mk 14:62; 16:19; Lk 22:69; Acts 7:55,56, Ro 8:34 [note]; Eph 1:20 [note]; Col 3:1 [note]; 1 Pet 3:22 [note] and the 4 verses in Hebrews - see below.)

The writer of Hebrews obviously considers this teaching about the position of  Christ Jesus our Great High Priest at the right hand of His Father as very important for he records this truth four times, at the beginning, in the middle and toward the end of his epistle...

Hebrews 1:3 And He is the radiance of His glory and the exact representation of His nature, and upholds all things by the word of His power. When He had made purification of sins, He sat down at the right hand of the Majesty on high

Hebrews 1:13 But to which of the angels has He ever said, "SIT AT MY RIGHT HAND, UNTIL I MAKE THINE ENEMIES A FOOTSTOOL FOR THY FEET"?

Hebrews 8:1 Now the main point in what has been said is this: we have such a High Priest, Who has taken His seat at the right hand of the throne of the Majesty in the heavens

Hebrews 12:2 fixing our eyes on Jesus, the Author and Perfecter of faith, Who for the joy set before Him endured the cross, despising the shame, and has sat down at the right hand of the throne of God.

Marvin Vincent paraphrases this verse as

"while the Pharisees were gathered together, Jesus asked them a question, saying, “What do you think about the Christ, whose son is He?” (Whose Son is the Messiah? Note He did not ask them as He had His disciples "Who do you say that I am" Mt 16:15 for the Pharisees were neither sympathetic or honest in their assessment of His credentials) They said to Him, “The son of David.” (the Pharisees knew that the Messiah must come from the line of David as His "son" and no doubt they could have quoted several OT passages to support their answer as eg 2Sa 7:12-13) He said to them (and in Jesus' second question He quotes Ps110:1 which every orthodox Jewish scholar interpreted as a reference to the Messiah. Only the Messiah could sit at the right hand of Jehovah God) “Then how does David in the Spirit call Him ‘Lord,’ saying,  ‘The Lord said to my Lord, ”Sit at My right hand, until I put Thine enemies beneath Thy feet” ‘?  “If David then calls Him ‘Lord,’ how is He his son?” And no one was able to answer Him a word, nor did anyone dare from that day on to ask Him another question." “If Messiah is David’s Son,” Jesus asked, “then how could Messiah also be David’s Lord?”

There is only one answer to this question. As God, Messiah is David’s Lord but as man, He is David’s Son. He is both “the root and the offspring of David” (Rev 22:6-note). Ps 110:1 teaches the deity and the humanity of Messiah. He is David’s Lord and He is David’s Son. The rulers had heard the multitudes proclaim Him as “Son of David” when He rode into Jerusalem. The fact that He accepted this title is evidence that Jesus acknowledged Himself to be the Messiah, the Son of God.  So once again the writer of Hebrews proves the superiority of Jesus for there was never an angel to which God said "Sit at My right hand..."