Old Testament readings use the Septuagint , the Scripture the apostles quoted. Masoretic numbering shown for reference.Learn why
LXX

Genesis 17:19

And God said to Abraam, Yea, behold, Sarrha thy wife shall bear thee a son, and thou shalt call his name Isaac; and I will establish my covenant with him, for an everlasting covenant, to be a God to him and to his seed after him.

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