Thematic Bible: Her miraculous conception of isaac

Then 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 indeed I will give you a son by her Then I will bless her, and she shall be a mother of nations; kings of peoples will come from her." Then Abraham fell on his face and laughed, and said in his heart, "Will a child be born to a man one hundred years old? And will Sarah, who is ninety years old, bear a child?" read more.
And Abraham said to God, "Oh that Ishmael might live before You!" But God said, "No, but Sarah your wife will bear you a son, and you shall call his name Isaac; and I will establish My covenant with him for an everlasting covenant for his descendants after him. "As for Ishmael, I have heard you; behold, I will bless him, and will make him fruitful and will multiply him exceedingly He shall become the father of twelve princes, and I will make him a great nation. "But My covenant I will establish with Isaac, whom Sarah will bear to you at this season next year."

Then they said to him, "Where is Sarah your wife?" And he said, "There, in the tent." He said, "I will surely return to you at this time next year; and behold, Sarah your wife will have a son." And Sarah was listening at the tent door, which was behind him. Now Abraham and Sarah were old, advanced in age; Sarah was past childbearing. read more.
Sarah laughed to herself, saying, "After I have become old, shall I have pleasure, my lord being old also?" And the LORD said to Abraham, "Why did Sarah laugh, saying, 'Shall I indeed bear a child, when I am so old?' "Is anything too difficult for the LORD? At the appointed time I will return to you, at this time next year, and Sarah will have a son." Sarah denied it however, saying, "I did not laugh"; for she was afraid. And He said, "No, but you did laugh."