18 “Then when Mary had come where Jesus was, and saw Him, she fell down at His feet, saying unto Him, Lord, if You had been here, my brother had not died. When Jesus therefore saw her weeping, and the Jews also weeping, who were with her, He groaned in the spirit, and troubled Himself, and said, Where have ye laid him?” Something there is, did we but know it, that He has suggested to us by groaning in the spirit, and troubling Himself. For who could trouble Him, save He Himself?
Therefore, my brethren, first give heed here to the power that did so, and then look for the meaning. You are troubled against your will; Christ was troubled because He willed. Jesus hungered, it is true, but because He willed; Jesus slept, it is true, but because He willed; He was sorrowful, it is true, but because He willed; He died, it is true, but because He willed: in His own power it lay to be thus and thus affected or not. For the Word assumed soul and flesh, fitting on Himself our whole human nature in the oneness of His person.
For the soul of the apostle was illuminated by the Word; so was the soul of Peter, the soul of Paul, of the other apostles, and the holy prophets—the souls of all were illuminated by the Word; but of none was it said, “The Word was made flesh;” of none was it said, I and the Father are one. The soul and flesh of Christ is one person with the Word of God, one Christ. And by this [Word] wherein resided the supreme power, was infirmity made use of at the beck of His will; and in this way “He troubled Himself.”
Source: Tractates on the Gospel of John (New Advent)