2 Samuel 17:24-26

24Then David came to Mahanaim. And Absalom crossed over the Jordan, he and all the men of Israel with him.

25Absalom put Amasa in command of the army instead of Joab. Now Amasa was the son of a man named Ithra the Israelite, who had married Abigail the daughter of Nahash, [the half sister of David and] the sister of Zeruiah, Joab’s mother.

26So Israel and Absalom camped in the land of Gilead.