2 Samuel 10:7-10

7On hearing this, David sent Joab out with the entire army of fighting men. 8The Ammonites came out and drew up in battle formation at the entrance of their city gate, while the Arameans of Zobah and Rehob and the men of Tob and Maakah were by themselves in the open country. 9Joab saw that there were battle lines in front of him and behind him; so he selected some of the best troops in Israel and deployed them against the Arameans. 10He put the rest of the men under the command of Abishai his brother and deployed them against the Ammonites.