Matthew Poole and continuators on 2 Samuel 18:7

7 Where the people of Israel were slain before the servants of David, and there was there a great slaughter that day of twenty thousand men.

i. e. The Soldiers of Absalom so called; partly, to note that all Israel (some few excepted) were ingaged in this Rebellion, which made David's deliverance more glorious and remarkable: and partly, in opposition to David's men, who, as to the main Body, or most considerable part, were of the Tribe of Iudah, or had followed him from Iudah.