7 Hear also what follows. “Therefore does my Father love me,” He says, “because I lay down my life, that I might take it again.” What is this that He says? “Therefore does my Father love me:” because I die, that I may rise again. For the “I” is uttered with special emphasis: “Because I lay down,” He says, “I lay down my life,” “I lay down.” What is that “I lay down”? I lay it down. Let the Jews no longer boast: they might rage, but they could have no power: let them rage as they can; if I were unwilling to lay down my life, what would all their raging effect?
By one answer of His they were prostrated in the dust: when they were asked, “Whom do you seek?” they said, “Jesus;” and on His saying to them, “I am He, they went backward, and fell to the ground.” Those who thus fell to the ground at one word of Christ when about to die, what will they do at the sound of His voice when coming to judgment? “I, I,” I say, “lay down my life, that I may take it again.” Let not the Jews boast, as if they had prevailed; He Himself laid down His life.
“I laid me down [to sleep],” He says [elsewhere]. You know the psalm: “I laid me down and slept; and I awaked [rose up], for the Lord sustains me.” What of that— “I lay down”? Because it was my pleasure, I did so. What does “I lay down” mean? I died. Was it not a lying down to sleep on His part, who, when He pleased, rose from the tomb as He would from a bed? But He loves to give glory to the Father, that He may stir us up to glorify our Creator. For in adding, “I arose, for the Lord sustains me;” think you there was here a kind of failing in His power, so that, while He had it in His own power to die, He had it not in His power to rise again?
So, indeed, the words seem to imply when not more closely considered. “I lay down to sleep;” that is, I did so, because I pleased. “And I arose:” why? “Because the Lord sustains [will sustain] me.” What then? Would Thou not have power to rise of Yourself? If You had not the power, You would not have said, “I have power to lay down my life, and I have power to take it again.” But, as showing that not only did the Father raise the Son, but the Son also raised Himself, hear how, in another passage in the Gospel, He says, “Destroy this temple, and in three days I will raise it up.”
And the evangelist adds: “But this He spoke of the temple of His body.” For only that which died was restored to life. The Word is not mortal, His soul is not mortal. If even yours dies not, could the Lord's be subject to death?
Source: Tractates on the Gospel of John (New Advent)