John Gill's  Exposition of the Bible 

2 Samuel 17:26

So Israel and Absalom pitched in the land of Gilead.

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.