Augustine of Hippo

"Dearly beloved, I write unto you no new commandment, but the old commandment which ye had from the beginning." What commandment calls he "old"? "Which ye had," saith he, "from the beginning. Old" then, in this regard, that ye have already heard it: otherwise he will contradict the Lord, where He saith, "A new commandment give I unto you, that ye love one another." But why an "old" commandment? Not as pertaining to the old man. But why? "Which ye had from the beginning. The old commandment is the word which ye have heard." Old then, in this regard, that ye have already heard it. And the selfsame he showeth to be new, saying, "Again, a new commandment write I unto you." Not another, but the selfsame which he hath called old, the same is also new. Why? "Which thing is true in Him and in you." Why old, ye have already heard: that is, because ye knew it already. But why new? "Because the darkness is past, and the true light now shineth." Lo, whence it is new: because the darkness pertains to the old man, but the light to the new man. What saith the Apostle Paul? "Put ye off the old man, and put ye on the new." And again what saith he? "Ye were sometime darkness, but now light in the Lord."