2 Samuel 18:1-2

1David numbered the men who were with him and set over them commanders of thousands and commanders of hundreds.

2Then David sent the army out, a third under the command of Joab, a third under Abishai the son of Zeruiah, Joab’s brother, and a third under the command of Ittai the Gittite. And the king said to the men, “I myself will certainly go out [to fight] with you.”