OT § 185

The Lord God said to Abraham: As for Sara your wife, her name shall not be called Sara, but Sarra shall be her name. I will bless her and will give you a child from her; and I will bless it and it shall be for nations and kings of nations will come from it. And Abraham fell on his face, and laughed and said in his mind; Shall a son be born in my hundredth year? And shall Sarra who is ninety bear a child? God said to Abraham: Yes; see, your wife Sarra will bear you a son and you will call his name Isaac; and I will establish my covenant with him as an everlasting covenant. Now Abraham and Sarra were old, advanced in years. But Sarra laughed to herself, saying: The thing has not happened to me until now; and my lord is old. And the Lord God said to Abraham: Why did Sarra laugh to herself, saying: Shall I really give birth? For I am aged. But nothing is impossible for God. And the Lord visited Sarra, as He had said, and she conceived and bore a son to Abraham in their old age at the time the Lord had said to him. But he circumcised him on the eighth day, as the Lord God had commanded him. And Abraham was a hundred when Isaac his son was born to him. But Sarra said: The Lord has given me laughter; for whoever hears will rejoice with me. And she said: Who will announce to Abraham that Sarra is suckling a child, for I have born a child in my old age? And the child grew and was weaned. And Abraham held a great banquet on the day his son Isaac was weaned.