On The Holy Trinity by St. Augustine
Chapter 2.--That Some Ways of Speaking Concerning the Son are to Be Understood According to Either Rule.
4. There are, then, some things in the sacred books, as I began by saying, so put, that it is doubtful to which they are to be referred: whether to that rule whereby the Son is less on account of His having taken the creature; or whether to that whereby it is intimated that although equal, yet He is of the Father. And in my opinion, if this is in such way doubtful, that which it really is can neither be explained nor discerned, then such passages may without danger be understood according to either rule, as that, for instance, |My doctrine is not mine, but His that sent me.| For this may both be taken according to the form of a servant, as we have already treated it in the former book; or according to the form of God, in which He is in such way equal to the Father, that He is yet of the Father. For according to the form of God, as the Son is not one and His life another, but the life itself is the Son; so the Son is not one and His doctrine another, but the doctrine itself is the Son. And hence, as the text, |He hath given life to the Son,| is no otherwise to be understood than, He hath begotten the Son, who is life; so also when it is said, He hath given doctrine to the Son, it may be rightly understood to mean, He hath begotten the Son, who is doctrine so that, when it is said, |My doctrine is not mine, but His who sent me,| it is so to be understood as if it were, I am not from myself, but from Him who sent me.