2 Samuel 10:10-14
10:10 He put his brother Abishai in charge of the rest of the army and they were deployed against the Ammonites.
10:11 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.
10:12 Be strong! Let’s fight bravely for the sake of our people and the cities of our God! The Lord will do what he decides is best!”
10:13 So Joab and his men marched out to do battle with the Arameans, and they fled before him.
10:14 When the Ammonites saw the Arameans flee, they fled before his brother Abishai and went into the city. Joab withdrew from fighting the Ammonites and returned to Jerusalem.