1 Chronicles 19:9-12

19:9 The Ammonites marched out and were deployed for battle at the entrance to the city, while the kings who had come were by themselves in the field. 19:10 When Joab saw that the battle would be fought on two fronts, he chose some of Israel’s best men and deployed them against the Arameans. 19:11 He put his brother Abishai in charge of the rest of the army and they were deployed against the Ammonites. 19:12 Joab said, “If the Arameans start to overpower me, you come to my rescue. If the Ammonites start to overpower you, I will come to your rescue.