Augustine of Hippo — as excerpted in the Catena Aurea on John 1:1

“(xv. de Trin. c. 22. [xiii.]) As our knowledge differs from God’s, so does our word, which arises from our knowledge, differ from that Word of God, which is born of the Father’s essence; we might say, from the Father’s knowledge, the Father’s wisdom, or, more correctly, the Father Who is Knowledge, the Father Who is Wisdom. (c. 23. (xiv.)) The Word of God then, the Only-Begotten Son of the Father, is in all things like and equal to the Father; being altogether what the Father is, yet not the Father; because the one is the Son, the other the Father. And thereby He knoweth all things which the Father knoweth; yet His knowledge is from the Father, ever as is His being: for knowing and being are the same with Him; and so as the Father’s being is not from the Son, so neither is His knowing. Wherefore the Father begat the Word equal to Himself in all things as uttering forth Himself. For had there been more or less in His Word than in Himself, He would not have uttered Himself fully and perfectly. With respect however to our own inner word, which we find, in whatever sense, to be like the Word, let us not object to see how very unlike it is also. (cap. 25. (xv.)) A word is a formation of our mind going to take place, but not yet made, and something in our mind which we toss to and fro in a slippery circuitous way, as one thing and another is discovered, or occurs to our thoughts. When this, which we toss to and fro, has reached the subject of our knowledge, and been formed therefrom, when it has assumed the most exact likeness to it, and the conception has quite answered to the thing; then we have a true word. Who may not see how great the difference is here from that Word of God, which exists in the Form of God in such wise, that It could not have been first going to be formed, and afterwards formed, nor can ever have been unformed, being a Form absolute, and absolutely equal to Him from Whom It is. Wherefore in speaking of the Word of God here nothing is said about thought in God; lest we should think there was any thing revolving in God, which might first receive form in order to be a Word, and afterwards lose it, and be carried round and round again in an unformed state.”