Genesis 15:1-6

1 After these things the word of the Lord came to Abram in a vision, "Do not be afraid, Abram, I am your shield; your reward shall be very great."
2 But Abram said, "O Lord God, what will you give me, for I continue childless, and the heir of my house is Eliezer of Damascus?"
3 And Abram said, "You have given me no offspring, and so a slave born in my house is to be my heir."
4 But the word of the Lord came to him, "This man shall not be your heir; no one but your very own issue shall be your heir."
5 He brought him outside and said, "Look toward heaven and count the stars, if you are able to count them." Then he said to him, "So shall your descendants be."
6 And he believed the Lord; and the Lord reckoned it to him as righteousness.