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."
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?"
References for Genesis 15:2
And Abram said, "You have given me no offspring, and so a slave born in my house is to be my heir."
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."