John Gill Commentary 2 Samuel 17:26

"And Israel and Absalom encamped in the land of Gilead." — 2 Samuel 17:26 (ASV)

So Israel and Absalom pitched in the land of Gilead .
] Which belonged to the tribes of Reuben and Gad, and the half tribe of Manasseh; here the Israelites that were with Absalom encamped, in order to give battle to David and his men.