2 Samuel 10:9-11

9When Joab saw that there was a battle line against him front and rear, he chose of all the best troops of Israel and arrayed them against the Arameans,

10but the rest of the troops he committed to the command of his brother Abishai, and he arrayed them against the children of Ammon.

11Then he said, “If the Arameans are too strong for me, then you will help me, but if the children of Ammon are too strong for you, then I will come to help you.