Thematic Bible: Her miraculous conception of isaac

And God said to Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be. And I will bless her, and give thee a son also by her: yea, I will bless her, and she shall be a mother of nations; kings of people shall proceed from her. Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born to him that is a hundred years old? and shall Sarah, who is ninety years old, bear? read more.
And Abraham said to God, O that Ishmael might live before thee! And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him. And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation. But my covenant will I establish with Isaac, whom Sarah shall bear to thee at this set time in the next year.

And they said to him, Where is Sarah thy wife? And he said, Behold, in the tent. And he said, I will certainly return to thee according to the time of life; and lo, Sarah thy wife shall have a son. And Sarah heard it in the tent door, which was behind him. Now Abraham and Sarah were old and far advanced in age; and it ceased to be with Sarah after the manner of women. read more.
Therefore Sarah laughed within herself, saying, After I am become old shall I have pleasure, my lord being old also? And the LORD said to Abraham, Why did Sarah laugh, saying, Shall I certainly bear a child, who am old? Is any thing too hard for the LORD? At the time appointed I will return to thee, according to the time of life, and Sarah shall have a son. Then Sarah denied, saying, I laughed not; for she was afraid. And he said, Nay; but thou didst laugh.