Genesis 15:2-4

2But Abram replied, “O Sovereign Lord, what good are all your blessings when I don’t even have a son? Since you’ve given me no children, Eliezer of Damascus, a servant in my household, will inherit all my wealth.

3You have given me no descendants of my own, so one of my servants will be my heir.”

4Then the Lord said to him, “No, your servant will not be your heir, for you will have a son of your own who will be your heir.”