linguistic:paraphrasing, structural:summarization
Isaac

As had been prophesied in Mamre the previous year, Sarah became pregnant and bore a son to Abraham, on the first anniversary of the covenant of circumcision. Abraham was "an hundred years old", when his son whom he named Isaac was born; and he circumcised him when he was eight days old. For Sarah, the thought of giving birth and nursing a child, at such an old age, also brought her much laughter, as she declared, "God hath made me to laugh, so that all who hear will laugh with me." Isaac continued to grow and on the day he was weaned, Abraham held a great feast to honor the occasion. During the celebration, however, Sarah found Ishmael mocking; an observation that would begin to clarify the birthright of Isaac.