As the story goes in Genesis 18, God came to Abraham when he was a hundred years old and told him that he and his wife, Sarah, would have a son. Incredulously, Sarah laughed. What a ridiculous idea! She was ninety years old and Abraham, one hundred!
God’s response (read the whole story and particularly verse 14):Genesis 18:10-14.
10 I will certainly return to you according to the time of life; and, see, Sarah your wife shall have a son. And Sarah heard it in the tent door, which was behind him.
11 Now Abraham and Sarah were old and well stricken in age; and it ceased to be with Sarah after the manner of women.
12 Therefore Sarah laughed within herself, saying, After I am waxed old shall I have pleasure, my lord being old also?
13 And the LORD said to Abraham, Why did Sarah laugh, saying, Shall I of a surety bear a child, which am old?
14 Is any thing too hard for the LORD? At the time appointed I will return to you, according to the time of life, and Sarah shall have a son.
See also Jeremiah 32:17,26,27.