Genesis 15:2-5

15:2 But Abram said, “O sovereign Lord, what will you give me since I continue to be childless, and my heir is Eliezer of Damascus?” 15:3 Abram added, “Since you have not given me a descendant, then look, one born in my house will be my heir!”

15:4 But look, the word of the Lord came to him: “This man will not be your heir, but instead a son who comes from your own body will be your heir.” 15:5 The Lord took him outside and said, “Gaze into the sky and count the stars – if you are able to count them!” Then he said to him, “So will your descendants be.”