Look back at Abraham your father, and Sarah who gave birth to you. When I called him, he was only one man, but then I blessed him and he had many descendants.
The descendants of Judah, men aged twenty or older, were recorded by name according to the genealogical records of their tribe and families. All those registered who could serve in the army
God also gave Abraham the agreement regarding circumcision, and so when Isaac was born, Abraham circumcised him on the eighth day. Isaac was the father of Jacob, and Jacob the father of the twelve patriarchs.
By her trust in God even Sarah herself was given the ability to conceive a child though she was too old, because she trusted God who had made the promise.