Genesis 15:1-6

After this, the word of the LORD came to Abram in a vision: ‘Do not be afraid, Abram. I am your shield, your very great reward.’ But Abram said, ‘Sovereign LORD, what can you give me since I remain childless and the one who will inherit my estate is Eliezer of Damascus?’ And Abram said, ‘You have given me no children; so a servant in my household will be my heir.’ Then the word of the LORD came to him: ‘This man will not be your heir, but a son who is your own flesh and blood will be your heir.’ He took him outside and said, ‘Look up at the sky and count the stars – if indeed you can count them.’ Then he said to him, ‘So shall your offspring be.’ Abram believed the LORD, and he credited it to him as righteousness.