9 But see what answer the Lord gave to their dull apprehension. He saw that they could not bear the brilliance of the truth, and He tempered it with words. “Is it not written in your law,” that is, as given to you, “that I said, You are gods?” And the Lord called all the Scriptures generally, the law: although elsewhere He speaks more definitely of the law, distinguishing it from the prophets; as it is said, “The law and the prophets were until John;” and “On these two commandments hang all the law and the prophets.” Sometimes, however, He divided the same Scriptures into three parts, as where He says, “All things must be fulfilled which were written in the law, and the prophets, and the psalms, concerning me.” But now He includes the psalms also under the name of the law, where it is written, “I said, You are gods.
If He calls them gods, to whom the word of God came, and the Scripture cannot be broken: say ye of Him, whom the Father has sanctified, and sent into the world, Thou blaspheme; because I said, I am the Son of God?” If the word of God came to men, that they might be called gods, how can the very Word of God, who is with God, be otherwise than God? If by the word of God men become gods, if by fellowship they become gods, can He by whom they have fellowship not be God? If lights which are lit are gods, is the light which enlightens not God?
If through being warmed in a way by saving fire they are constituted gods, is He who gives them the warmth other than God? Thou approachest the light and art enlightened, and numbered among the sons of God; if you withdraw from the light, you fall into obscurity, and art accounted in darkness; but that light approaches not, because it never recedes from itself. If, then, the word of God makes you gods, how can the Word of God be otherwise than God? Therefore did the Father sanctify His Son, and send Him into the world.
Perhaps some one may be saying: If the Father sanctified Him, was there then a time when He was not sanctified? He sanctified in the same way as He begot Him. For in the act of begetting He gave Him the power to be holy, because He begot Him in holiness. For if that which is sanctified was unholy before, how can we say to God the Father, “Hallowed be Your name”?
Source: Tractates on the Gospel of John (New Advent)