4 And then, what follows? “I must work the works of Him that sent me.” See, here is that sent one [Siloam], wherein the blind man washed his face. And see what He said: “I must work the works of Him that sent me, while it is day.” Recall to your mind the way in which He gives universal glory to Him of whom He is: for that One has the Son who is of Him; He Himself has no One of whom He is. But wherefore, Lord, said You, “While it is day”? Hearken why He did so. “The night comes when no man can work.” Not even Thou, Lord. Will that night have such power that not even Thou, whose work the night is, will be able to work therein? For I think, Lord Jesus, nay I do not think, but believe and hold it sure, that You were there when God said, “Let there be light, and there was light.” For if He made it by the Word, He made it by You: and therefore it is said, “All things were made by Him; and without Him was nothing made.” “God divided between the light and the darkness: the light He called Day, and the darkness He called Night.”
Source: Tractates on the Gospel of John (New Advent)