Genesis 15:4-5

4Then behold, the word of the Lord came to him, saying, “This man will not be your heir; 1but one who will come from your own 2body shall be your heir.”

5And He took him outside and said, “Now look toward the heavens and 3count the stars, if you are able to count them.” And He said to him, “4So shall your 5descendants be.”