Anti-pelagian Writings by St. Augustine
Chapter 12.--The Old Testament is Properly One Thing--The Old Instrument Another.
Therefore, by a custom of speech already prevailing, in one way the law and all the prophets who prophesied until John are called the |Old Testament;| although this is more definitely called the |Old Instrument| rather than the |Old Testament;| but this name is used in another way by the apostolical authority, whether expressly or impliedly. For the apostle is express when he says, |Until this day, as long as Moses is read, remaineth the same veil in the reading of the old testament; because it is not revealed, because it is made of no effect in Christ.| For thus certainly the old testament referred to the ministry of Moses. Moreover, he says, |That we should serve in the newness of the Spirit, and not in the oldness of the letter,| signifying that same testament under the name of the letter. In another place also, |Who also hath made us able ministers of the new testament; not of the letter, but of the Spirit: for the letter killeth, but the Spirit maketh alive.| And here, by the mention of the new, he certainly meant the former to be understood as the old. But much more evidently, although he did not say either old or new, he distinguished the two testaments and the two sons of Abraham, the one of the bondwoman, the other of the free, as I have above mentioned. For what can be more express than his saying, |Tell me, ye that desire to be under the law, have ye not heard the law? For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman. But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise. Which things are in allegory; for these are the two testaments; the one in the Mount Sinai, gendering to bondage, which is Agar. For Sinai is a mountain in Arabia, which is associated with Jerusalem which now is, for it is in bondage with her children. But Jerusalem that is above is free, which is our mother?| What is more clear, what more certain, what more remote from all obscurity and ambiguity to the children of the promise? And a little after, |Now we, brethren, as Isaac was, are the children of promise.| Also a little after, |But we, brethren, are not children of the bondwoman, but of the free,| with the liberty with which Christ has made us free. Let us, therefore, choose whether to call the righteous men of old the children of the bondwoman or of the free. Be it far from us to say, of the bondwoman; therefore if of the free, they pertain to the new testament in the Holy Spirit, whom, as making alive, the apostle opposes to the killing letter. For on what ground do they not belong to the grace of the new testament, from whose words and looks we convict and rebut such most frantic and ungrateful enemies of the same grace as these?