Genesis 15:2-5

But Abram said, “Lord GOD, what will You give me, seeing I go childless, and the heir of my house is Eliezer of Damascus?” Then Abram said, “Look, You have given me no offspring; indeed one born in my house is my heir!” And behold, the word of the LORD came to him, saying, “This one shall not be your heir, but one who will come from your own body shall be your heir.” Then He brought him outside and said, “Look now toward heaven, and count the stars if you are able to number them.” And He said to him, “So shall your descendants be.”