2 Samuel 18:5-7

And the king commanded Joab and Abishai and Ittai, saying, Deal gently for my sake with the young man, even with Absalom. And all the people heard when the king gave all the captains charge concerning Absalom. So the people went out into the field against Israel: and the battle was in the forest of Ephraim. And the people of Israel were smitten there before the servants of David, and there was a great slaughter there that day of twenty thousand men.