2 And then expanding still further how it was that the Father should be glorified by the Son, He says: “As You have given Him power over all flesh, that He should give eternal life to all that You have given Him.” By all flesh, He meant every man, signifying the whole by a part; as, on the other hand, the whole man is signified by the superior part, when the apostle says, “Let every soul be subject to the higher powers.” For what else did He mean by “every soul,” save every man? And this, therefore, that power over all flesh was given to Christ by the Father, is to be understood in respect of His humanity; for in respect of His Godhead all things were made by Himself, and in Him were created all things in heaven and in earth, visible and invisible. “As,” then, He says, “You have given Him power over all flesh,” so may Your Son glorify You, in other words, make You known to all flesh whom You have given Him. For You have so given, “that He should give eternal life to all that You have given Him.”
Source: Tractates on the Gospel of John (New Advent)