Genesis 14:13-14

Then one who had escaped came and told Abram the Hebrew, who was living by the oaks of Mamre the Amorite, brother of Eshcol and of Aner. These were allies of Abram. When Abram heard that his kinsman had been taken captive, he led forth his trained men, born in his house, 318 of them, and went in pursuit as far as Dan.