Genesis 17:19-21

19God said, “No, but aSarah your wife shall bear you a son, and you shall call his name bIsaac.
 Isaac means he laughs
I will establish my covenant with him as an everlasting covenant for his offspring after him.
20As for Ishmael, I have heard you; behold, I have blessed him and will make him fruitful and dmultiply him greatly. He eshall father twelve princes, and fI will make him into a great nation. 21But gI will establish my covenant with Isaac, hwhom Sarah shall bear to you at this time next year.”

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