Genesis 15:5-6

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.

Genesis 15:16

15:16 In the fourth generation your descendants will return here, for the sin of the Amorites has not yet reached its limit.”