Genesis 14:13-14

13One of the survivors came and told Abram the Hebrew, who lived near the oaks belonging to Mamre the Amorite, the brother of Eshcol and the brother of Aner. They were bound by a treaty with Abram.

14When Abram heard that his relative had been taken prisoner, he assembled his 318 trained men, born in his household, and they went in pursuit as far as Dan.