Anti-pelagian Writings by St. Augustine
Chapter 8.--All Righteous Men Before and After Abraham are Children of the Promise and of Grace.
Whether, then, Abraham, or righteous men before him or after him, even to Moses himself, by whom was given the testament gendering to bondage from Mount Sinai, or the rest of the prophets after him, and the holy men of God till John the Baptist, they are all children of the promise and of grace according to Isaac the son of the freewoman, -- not of the law, but of the promise, heirs of God and joint-heirs with Christ. Far be it from us to deny that righteous Noah and the righteous men of the earlier times, and whoever from that time till the time of Abraham could be righteous, either manifestly or hiddenly, belong to the Jerusalem which is above, who is our mother, although they are found to be earlier in time than Sarah, who bore the prophecy and figure of the free mother herself. How much more evidently, then, after Abraham, to whom that promise was declared, that he should be called the father of many nations, must all, whoever have pleased God, be esteemed the children of the promise! For from Abraham, and the righteous men who followed him, the generation is not found more true, but the prophecy more plain.