14 “I cannot of myself do anything; as I hear I judge, and my judgment is just.” If as You hear You judge, of whom dost Thou hear? If of the Father, yet surely “the Father judges not any man, but has given all judgment to the Son.” When do You, being in a manner the Father's herald, declare what You hear? I speak what I hear, because what the Father is, that I am: for, indeed, speaking is my function; because I am the Father's Word. For this Christ says to you. Thereupon, of yours.
What is “As I hear I judge,” but “As I am”? For in what manner does Christ hear? Let us inquire, brethren, I beg of you. Does Christ hear of the Father? How does the Father speak to Him? Undoubtedly, if He speaks to Him, He uses words to Him; for every one who says something to any one, says it by a word. How does the Father speak to the Son, seeing that the Son is the Father's Word? Whatever the Father says to us, He says it by His Word: the Word of the Father is the Son; by what other word, then, does He speak to the Word Himself?
God is one, has one Word, contains all things in one Word. What does that mean, then, “As I hear, I judge?” Just as I am of the Father, so I judge. Therefore “my judgment is just.” If You do nothing of Yourself, O Lord Jesus, as carnal men think; if You do nothing of Yourself, how did You say a while before, “So also the Son quickens whom He will”? Just now You say, Of myself I do nothing. But what does the Son declare, but that He is of the Father? He that is of the Father is not of Himself. If the Son were of Himself, He would not be the Son: He is of the Father. That the Father is, is not of the Son; that the Son is, is of the Father. Equal to the Father; but yet the Son of the Father, not the Father of the Son.
Source: Tractates on the Gospel of John (New Advent)