2nd Samuels 5:22-24

Once again the Philistines came up, and were spread out in the valley of Rephaim. When David inquired of the Lord, he said, ‘You shall not go up; go round to their rear, and come upon them opposite the balsam trees. When you hear the sound of marching in the tops of the balsam trees, then be on the alert; for then the Lord has gone out before you to strike down the army of the Philistines.’ David did just as the Lord had commanded him; and he struck down the Philistines from Geba all the way to Gezer.