Genesis 15:4-6

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.”

15:6 Abram believed the Lord, and the Lord considered his response of faith as proof of genuine loyalty.