And Isaac entreated the LORD for his wife, because she was barren: and the LORD was entreated of him, and Rebekah his wife conceived.
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These things are told for our benefit so that we may give evidence of much goodwill and not pry into God’s plans. Yet we need to explain the reason why these women were barren. What, then, is the reason? So that when you see the Virgin giving birth to our common Lord you may not be incredulous. Exercise your mind, it is saying, on the womb of these sterile women, so that when you see an infertile and sealed womb opened for childbearing by God’s grace, you may not be surprised to hear that a maiden gave birth. Or rather, feel surprise and amazement but don’t refuse faith in the marvel. So when the Jew says, “How did the Virgin give birth?” say to him, “How did the sterile old woman give birth?” In that case, you see, there were two impediments, her advanced age and the imperfect condition of nature, whereas with the Virgin there was one impediment, her not having experienced marriage. Consequently the barren woman prepares the way for the virgin.