1 Samuel 7:3-6, 10

Then Samuel said to all the people of Israel, “If you want to return to the LORD with all your hearts, get rid of your foreign gods and your images of Ashtoreth. Turn your hearts to the LORD and obey him alone; then he will rescue you from the Philistines.” So the Israelites got rid of their images of Baal and Ashtoreth and worshiped only the LORD. Then Samuel told them, “Gather all of Israel to Mizpah, and I will pray to the LORD for you.” So they gathered at Mizpah and, in a great ceremony, drew water from a well and poured it out before the LORD. They also went without food all day and confessed that they had sinned against the LORD. (It was at Mizpah that Samuel became Israel’s judge.)

Just as Samuel was sacrificing the burnt offering, the Philistines arrived to attack Israel. But the LORD spoke with a mighty voice of thunder from heaven that day, and the Philistines were thrown into such confusion that the Israelites defeated them.