1 Samuel 7:6,10 (NIV)
6 When they had assembled at Mizpah, they drew water and poured it out before the LORD. On that day they fasted and there they confessed, "We have sinned against the LORD." And Samuel was leader of Israel at Mizpah.
10 While Samuel was sacrificing the burnt offering, the Philistines drew near to engage Israel in battle. But that day the LORD thundered with loud thunder against the Philistines and threw them into such a panic that they were routed before the Israelites.