The book of Hebrews places great emphasis upon the work of the Trinity in the redemption of sinners. In this particular instance, we see that God speaks as a Trinity: the Father is portrayed as declaring the Son’s advent through the prophets and speaking to us through His Son; the Son is described as declaring the Gospel to us; and the Holy Spirit is shown to be calling sinners to repent, to trust and rest in Christ. The economic interrelations within the Godhead are here, I think, beautifully placed on display, as the Father speaks of the Son (1:1-6, 8-13), the Son speaks of the Father (2:12-13), and the Holy Spirit speaks of the rest that is offered to us in Christ our Lord (3:7-11).
But this isn’t the only place where we see this occur. Throughout the book of Hebrews, we encounter each Person of the Godhead speaking in a manner that corresponds to the economical function/role He exhibits in relation to the Other Two. Here is a brief summary table:
|Speaks of the Son, whom He begot, and appointed as heir of all things (1:1-13)
Speaks of appointing the Son to be a priest forever after the order of Melchizedek (5:5-6)
Speaks in Genesis 22:17 to Abraham, promising him descendents. (6:13-14)
Speaks to Moses about the building of the tabernacle. (8:5)
Speaks about the New Covenant to supersede/complete the Old Covenant (8:8-13)
Speaks to Abraham about his descendents coming through Isaac (11:18)
Speaks of what is to be done to anything /anyone that comes close to the Mountain (12:20)
Speaks of the coming final judgment of all men (12:26)
Speaks to us, assuring us of His eternal presence with us (13:5)
|Speaks of His preaching ministry and His perfect trust in the Father, as well as His possession of His people (2:10-13)
Speaks of His self-sacrifice as our sacrifice (10:5-7)
[Christ appears to Abraham, at least typologically, in the person of Melchizedek, 7.]
[Christ appears the Greater Mediator of the New Covenant in contrast to Moses, 8:4-6 ]
[Christ is the Seed of Abraham, 2:11-17.]
[The Mediatorial work of Christ is contrasted with the Mediatorial work of Moses, 12:21-24.]
[Which will be worked through Christ, the Judge of the living and the dead, 9:27-28]
[Christ is spoken of as sharing, with the Father, immutability, 13:8]
|Speaks of sin (in rejecting the Gospel) and righteousness (in resting in Christ’s finished work) (3:7-11)
Speaks of His regenerative work in the believer (10:15-17)
We see in this epistle, then, a consistent pattern: The Father plans, appoints, and decrees; the Son does the will of the Father, suffers for sinners, acts on their behalf as Mediator, and will return as Judge; the Holy Spirit convicts of sin and of righteousness, regenerates sinners, and applies the work of Christ to them. Is this not what we encounter in our Lord’s farewell/upper room discourse in John 14-16? An exhaustive study is not possible here, but I hope to do one in the future.
 What is beautiful about the apostle’s quotation is that it is from the Sacrifice of Isaac narrative, where the Lord promises to provide (i.)the Substitutionary Lamb, and (ii.)many descendents of Abraham, of whom the Lord says: “Now I know that you fear God, seeing you have not withheld your son, your only son, from Me” (Gen. 22:12) In one passage we have first the promise of the Sacrifice and the promise of descendents of the man of faith. Paul, therefore, is not reading into the Old Testament when he says that “if you are Christ’s, then you are Abraham’s offspring, heirs according to the promise” (Gal. 3:29), for the promise of the Messiah and descendents comes directly on the heels of Abraham’s evidence of faith.