Genesis 15:4-6

Then behold, the word of the LORD came to him, saying, “This man will not be your heir; but one who will come forth from your own body, he shall be your heir.” And He took him outside and said, “Now look toward the heavens, and count the stars, if you are able to count them.” And He said to him, “So shall your descendants be.” Then he believed in the LORD; and He reckoned it to him as righteousness.