Genesis 15:3-6

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.” And he believed in the LORD, and He accounted it to him for righteousness.