Aliya Summary: G‑d sealed a covenant with Avraham and his descendants; the sign of the covenant is the circumcision of all males when they are eight days old. Sarai’s name is changed to Sarah, and G‑d promises a delighted Abraham that he will father another son, this time from Sarah. At the age of 99, Abraham circumcised himself, his son Ishmael, and all the members of his household.
When Avraham finds out that he will have a son, Yitzchak, he laughs. Sarah laughed too, but her laughter was one of disbelief, while Avraham’s was one of happiness. It’s interesting to note that Yitzchak was named so because of Avraham’s reaction, not Sarah’s.