1 Kings 16:15-17

15In the twenty-seventh year of Asa’s reign over Judah, Zimri reigned in Tirzah for seven days. Now the troops were encamped against Gibbethon of the Philistines, 16and the people in the camp heard that Zimri had conspired against the king and struck him down. So there in the camp that very day, all Israel proclaimed Omri, the commander of the army, king over Israel.

17Then Omri and all the Israelites marched up from Gibbethon and besieged Tirzah.