Numbers 21:1-2

Living Bible

21 When the king of Arad heard that the Israelis were approaching (for they were traveling the same route as the spies), he mobilized his army and attacked Israel, taking some of the men as prisoners. ² Then the people of Israel vowed to the Lord that if he would help them conquer the king of Arad and his people, they would completely annihilate all the cities of that area.