“Yahweh dealt with Sarah as he had said, and Yahweh did for Sarah as he had promised. Sarah conceived and bore Abraham a son in his old age, at the time of which God had spoken to him. Abraham gave the name Isaac to his son, whom Sarah bore him. Abraham circumcised his son Isaac when he was eight days old, as God had commanded him. Abraham was a hundred years old when his son Isaac was born to him. Now Sarah said, ‘God has made laughter for me. Everyone who hears will laugh with me.’ She said, ‘Who would ever have said to Abraham that Sarah would nurse children? Yet I have borne him a son in his old age.’”
Back to the main event, the birth of Isaac. Was this a miraculous birth? Now Yahweh dealt with Sarah so that she conceived and bore Abraham, at age 100, a son named Isaac, which refers to laughter. Isaac was circumcised when he was eight days old. Sarah said that everyone will now laugh with her because she has borne a child in her old age of 90.