And [God] made with Abraham a covenant (an agreement to be religiously observed) of which circumcision was the seal. And under these circumstances [Abraham] became the father of Isaac and circumcised him on the eighth day; and Isaac [did so] when he became the father of Jacob, and Jacob [when each of his sons was born], the twelve patriarchs. [Gen. 17:10-14; 21:2-4; 25:26; 29:31-35; 30:1-24; 35:16-26.]