Thomas asks whether the Father delivered the Son to the Passion (ST III, 47, 3). His answer is Yes, and he gives a proof text: Romans 8:32.
But the way he explicates that affirmative answer is worthy of attention. He starts by emphasizing that Christ “suffered voluntarily out of obedience to the Father.” He is not an unwilling victim of the Father’s scheme, but a willing participant.
Given this premise, there are three respects in which the Father gave up the Son to His suffering. First, since God eternally preordained Christ’s Passion for the salvation of humanity. Thomas cites Isaiah 53 in support. Second, the Father infused the Son with caritas (the Spirit?), and thus “inspired Him with the will to suffer for us.” Finally, He delivered Jesus up in the negative sense that He did not “shield” Him from death but abandoned Him to His persecutors.
To the objection that God would be wicked and cruel to deliver the innocent Jesus to torment, Thomas agrees, but insists that this is not what happened on the cross. “The Father did not so deliver up Christ, but inspired Him with the will to suffer for us.” This does indeed demonstrate God’s severity, since “He would not remit sin without penalty,” yet it demonstrates also His goodness, since God Himself bears the penalty.
To the objection that no one can be given to death both by himself and by another, Thomas replies that the will of the Son is the will of the Father: “Christ as God delivered Himself up to death by the same will and action as that by which the Father delivered Him up; but as man He gave Himself up by a will inspired of the Father.” There is no contradiction in saying both that the Father delivered Jesus and that Christ delivered Himself.
Thomas, in other words, presents an account of atonement that includes a penal element but does not bump up against the the Trinitarian objections that so often dog penal theories. He does it by insisting that the Father and Son are one in willing Jesus to go to His death.