Genesis 18:15 (KJV)

And he said, I will certainly return unto 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 well stricken in age; and it ceased to be with Sarah after the manner of women.

Therefore Sarah laughed within herself, saying, After I am waxed old shall I have pleasure, my lord being old also?

And the LORD said unto Abraham, Wherefore did Sarah laugh, saying, Shall I of a surety bear a child, which am old?

Is any thing too hard for the LORD? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son.

And the men rose up from thence, and looked toward Sodom: and Abraham went with them to bring them on the way.

And the LORD said, Shall I hide from Abraham that thing which I do;

Seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him?

For I know him, that he will command his children and his household after him, and they shall keep the way of the LORD, to do justice and judgment; that the LORD may bring upon Abraham that which he hath spoken of him.

And the LORD said, Because the cry of Sodom and Gomorrah is great, and because their sin is very grievous;