Thematic Bible: Her miraculous conception of isaac

And God said to Abraham, "As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. I will bless her, and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her." Then Abraham fell on his face and laughed and said to himself, "Shall a child be born to a man who is a hundred years old? Shall Sarah, who is ninety years old, bear a child?" read more.
And Abraham said to God, "Oh that Ishmael might live before you!" God said, "No, but Sarah your wife shall bear you a son, and you shall call his name Isaac. I will establish my covenant with him as an everlasting covenant for his offspring after him. As for Ishmael, I have heard you; behold, I have blessed him and will make him fruitful and multiply him greatly. He shall father twelve princes, and I will make him into a great nation. But I will establish my covenant with Isaac, whom Sarah shall bear to you at this time next year."

They said to him, "Where is Sarah your wife?" And he said, "She is in the tent." The LORD said, "I will surely return to you about this time next year, and Sarah your wife shall have a son." And Sarah was listening at the tent door behind him. Now Abraham and Sarah were old, advanced in years. The way of women had ceased to be with Sarah. read more.
So Sarah laughed to herself, saying, "After I am worn out, and my lord is old, shall I have pleasure?" The LORD said to Abraham, "Why did Sarah laugh and say, 'Shall I indeed bear a child, now that I am old?' Is anything too hard for the LORD? At the appointed time I will return to you, about this time next year, and Sarah shall have a son." But Sarah denied it, saying, "I did not laugh," for she was afraid. He said, "No, but you did laugh."