Genesis 14:13-14

13Then an escapee came and reported this to Abram the Hebrew. Now Abram was living near the Oaks1 of Mamre the Amorite, a brother of Eshcol and Aner, all of whom were bound by treaty2 to Abram. 14And when Abram heard that his relative had been captured, he mobilized the 318 trained men born in his household, and they set out in pursuit as far as Dan.