Genesis 15:1-2, 8

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?”

But Abram said, “Sovereign LORD, how can I know that I will gain possession of it?”