2 Samuel 5:22-25

22Once more the Philistines came up and spread out in the Valley of Rephaim; 23so David inquired of the Lord, and he answered, “Do not go straight up, but circle around behind them and attack them in front of the poplar trees. 24As soon as you hear the sound of marching in the tops of the poplar trees, move quickly, because that will mean the Lord has gone out in front of you to strike the Philistine army.” 25So David did as the Lord commanded him, and he struck down the Philistines all the way from Gibeonto Gezer.