Genesis 15:4-5

Then behold, the word of the LORD came to him, saying, “This man [Eliezer] will not be your heir but he who shall come from your own body shall be your heir.” And the LORD brought Abram outside [his tent into the night] and said, “Look now toward the heavens and count the stars—if you are able to count them.” Then He said to him, “So [numerous] shall your descendants be.” [Heb 11:12]