Williams marks a second ground for our union with Christ (the first was bearing the nature of humanity):
“The Incarnate Son of God, thus intimately allied to our race, offered up Himself as the Sacrifice for our sins. He bore, on His immaculate spirit, the pressure of our guilt, and submitted to death,—even the death of the cross,—that He might redeem and save us. It was, indeed, the grand and distinguishing feature of the mediatorial scheme, that the Redeemer, though Himself pure and spotless, should take the place of the guilty, and endure, in our stead, the penalty of sin.”
Henry Wilkinson Williams. “Union with Christ.” Note that Williams lists this as a ground of our union with Christ — but it is not properly a present aspect of the nature of union. Union concerns the present relationship between the believer and Jesus Christ. Union thus concerns Jesus as risen, exalted and enthroned — not as crucified. However, as will be explained below — this union is a real union with the crucified Christ, which takes place prior to his ascension and our existence (when John stood at the foot of the cross, he was not in union with Christ at that historical moment, because Holy Spirit had not yet been given. And yet the death of Christ becomes a ground for the future giving of the Spirit, and the subsequent union with the exalted Christ — which then works backward in time to be a real union).
Williams rightly links penal substitutionary atonement to union. However, Williams fails to work out the strongest case for the crucifixion and union. Williams sets forth the doctrine of substitutionary atonement in Paul — yet it is Peter who draws the strongest connection between Christ’s death and our present union.
A full exegesis of the relevant Scripture cannot be had here, but some outlines can be seen. First, Peter ties the living hope of inheritance and resurrection directly to the death and resurrection of Jesus Christ:
Blessed be the God and Father of our Lord Jesus Christ! According to his great mercy, he has caused us to be born again to a living hope through the resurrection of Jesus Christ from the dead,
1 Peter 1:3. One great element of union is the fact of resurrection — the resurrection of Jesus becomes the hope of our resurrection. Our being born again — the transformation of our humanity wrought by union flows from the resurrection.
In verses 8-9, Peter ties our present love and relationship to Jesus (now union is not a mere relationship of love, but it is not less than love) to our salvation — which Peter repeatedly ties to Christ’s death:
8 Though you have not seen him, you love him. Though you do not now see him, you believe in him and rejoice with joy that is inexpressible and filled with glory,
9 obtaining the outcome of your faith, the salvation of your souls.
It must be noted that Peter describes the love of Jesus to one whom we have not seen. While sight is not a necessary element of love, actual relationship must be an element of love — or love is either delusional or a matter of mere words (just sounds) without substance. We could not love nor believe were it not for the actual communication of Christ to — which communication arises from the sacrifice of Christ.
In 1:19, Peter states the sacrifice of Jesus as the basis of our atonement. Peter then goes onto state that our relationship to God is “through” Jesus (which although he does not articulate union at the very least presupposes union to make “through” an actual relationship:
20 He was foreknown before the foundation of the world but was made manifest in the last times for the sake of you
21 who through him are believers in God, who raised him from the dead and gave him glory, so that your faith and hope are in God.
Peter’s most detailed discussion of union comes in 2:4-5 – where Peter calls Christ a living stone who transforms us into living stones to be built into a “spiritual house”. In the place of describing Christ as living stone, Peter notes that Christ was the rejected stone — which refers to the crucifixion of Jesus (that Peter explicitly draws this connection can be seen in Acts 4:10-11):
4 As you come to him, a living stone rejected by men but in the sight of God chosen and precious, 5 you yourselves like living stones are being built up as a spiritual house, to be a holy priesthood, to offer spiritual sacrifices acceptable to God through Jesus Christ.
In 1 Peter 2:24, Peter again grounds union in the death of Christ. Here Peter ties our death to sin and life to righteous to the death of Jesus for our sin:
He himself bore our sins in his body on the tree, that we might die to sin and live to righteousness. By his wounds you have been healed.
This passage while not as explicit and detailed on the matter of union as Romans 6:3-11, still draws the crucifixion together with union.
Again in 3:18, Peter ties our being brought into relationship with God – a key element of union — directly to the sacrifice of Christ:
For Christ also suffered once for sins, the righteous for the unrighteous, that he might bring us to God, being put to death in the flesh but made alive in the spirit,
In short, Peter repeatedly grounds our union directly to the matter of Christ’s death. A similar analysis could be made of union in Romans 6:3-5:
3 Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death? 4 We were buried therefore with him by baptism into death, in order that, just as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life. 5 For if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his.
Here Paul explicitly ties the death of Jesus to union, drawing out a correspondence between the work of Christ and the redemption of the believer.
Williams’ point of the penal substitutionary atonement of Christ being a ground of union is certainly true — and he could have constructed a stronger case to that effect.
Williams does draw an additional element of Christ’s death as a ground for our union. Christ suffered the agony of the penalty for our sins — Christ was moving into the place of union with us — even though such union does not properly exist until the Holy Spirit apply the work to us — in the matter of his death. The agony of Christ demonstrates plainly the cost of the ground for our union:
A peculiar anguish oppressed the Redeemer’s spirit, all through these scenes of wonder and awe. How emphatic were His own words addressed to the three favoured disciples, when leaving them near the entrance of the garden of Gethsemane, that He might go forward, and alone pour out His soul to His Father:—” My soul is exceeding sorrowful, even unto death: tarry ye here, and watch with Me”! How affecting His reiterated prayer, that the “cup” of bitterness and trembling which He was then drinking might, if it were consistent with the Father’s will, and if it could be done without impairing the efficacy of His atonement, “pass” from Him! How impressive was His cry, uttered upon Calvary, just as the mysterious darkness cleared away, and when He was about to bow His head in death :— “My God, My God, why hast Thou forsaken Me”! Surely all this teaches us, that the Redeemer endured an inward and crushing anguish, far more terrible than the insults of His enemies, or the pain “and torture of crucifixion. There was “the travail of His soul,”—a sorrow such as He only knew, and He only could endure. And howcan we account for this, otherwise than by recognising the fact, that He was even then bearing the penalty of our sins, so far as to make it consistent with the full maintenance of the law, and the accomplishment of the highest ends of a moral administration, for God to accept and justify all who should embrace Him as their Saviour? How can we account for it, but by holding the truth, that, though Himself pure and spotless, He felt the pressure of our guilt even as if it had been. His own? We would not attempt minutely to pry into the peculiar nature of the Redeemer’s sorrows; but the sentiment which we have just expressed appears to us to be involved in the unequivocal statements of Holy Scripture, while it shows how intimate is the relation which subsists between the Saviour and all who come unto Him for life and peace.
ADDENDUM: Robert Letham in Union With Christ (P & R 2011) draws out this point, relying on Hugh Martin’s 19th century work on the atonement: Letham notes that while the Westminster divines tied the substitutionary work of the atonement to the eternal covenant of the Trinity (WLC Q 31). Letham quotes Martin, “He was substituted for us, because he is one with us” (Letham, 64).
Now we are one with him on the basis of our election “in him” that is in Christ (Eph. 1:4). The spiritual blessings procured by Christ and Christ become ours in this election. The election occurs before the foundation of the world; the benefits procured in history and beyond history (in the life, death, burial, resurrection, ascension and enthronement of Christ) becomes truly — such that even the death of Christ which occurs before us, becomes ours in Christ, freeing us from death.
The temporal complaint that I can be present in union with Christ in his death assumes that physical, contemporaneous time is an aspect of this eternal relationship which commences in a manner before my existence.
Thus, the atonement works with election and adoption to secure union and to be a benefit of union.