II. The two natures acted conjointly, and the human sufferings were not compulsory, but in accordance with the Divine will
But because the design of that mystery which was ordained for our restoration before the eternal ages, was not to be carried out without human weakness and without Divine power, both “form” does that which is proper to it in common with the other, the Word, that is, performing that which is the Word's and the flesh that which is of the flesh. One of them gleams bright with miracles, the other succumbs to injuries. The one departs not from equality with the Father's glory, the other leaves not the nature of our race. But nevertheless even His very endurance of sufferings does not so far expose Him to a participation in our humility as to separate Him from the power of the Godhead. All the mockery and insults, all the persecution and pain which the madness of the wicked inflicted on the Lord, was not endured of necessity, but undertaken of free-will: “for the Son of Man came to seek and to save that which had perished:” and He used the wickedness of His persecutors for the redemption of all men in such a way that in the mystery of His Death and Resurrection even His murderers could have been saved, if they had believed.
Source: Sermons (New Advent)