2 Samuel 10:9-11

9And Joab saw that the front of the battle was against him before and behind; and he chose out of all the choice men of Israel, and put them in array against the Syrians;

10and the rest of the people he gave into the hand of Abishai his brother that he might array them against the children of Ammon.

11And he said, If the Syrians be too strong for me, then thou shalt help me; and if the children of Ammon be too strong for thee, then I will come and help thee.