Genesis 17:19-21

Darby(i) 19 And God said, Sarah thy wife shall indeed bear thee a son; and thou shalt call his name Isaac; and I will establish my covenant with him, for an everlasting covenant for his seed after him. 20 And for Ishmael I have heard thee: behold, I will bless him, and will make him fruitful, and will very greatly multiply him; twelve princes shall he beget, and I will make him a great nation. 21 But my covenant will I establish with Isaac, whom Sarah shall bear to thee at this appointed time in the next year.