Genesis 15:2-5

2And Abram said, Lord Jehovah, what wilt thou give me? seeing I go childless, and the steward of my house is this Eliezer of Damascus.

3And Abram said, Lo, to me thou hast given no seed, and behold, a son of my house will be mine heir.

4And behold, the word of Jehovah [came] to him, saying, This shall not be thine heir, but he that will come forth out of thy body shall be thine heir.

5And he led him out, and said, Look now toward the heavens, and number the stars, if thou be able to number them. And he said to him, So shall thy seed be!