2 Samuel 17:24-26

About the time David arrived at Mahanaim, Absalom crossed the Jordan, and the whole army of Israel with him. Absalom had made Amasa head of the army, replacing Joab. (Amasa was the son of a man named Ithra, an Ishmaelite who had married Abigail, daughter of Nahash and sister of Zeruiah, the mother of Joab.) Israel and Absalom set camp in Gilead.