2 Samuel 5:22-25

Now the Philistines came up once again and spread themselves out in the valley of Rephaim. When David inquired of the LORD, He said, “You shall not go directly up; circle around behind them and come at them in front of the balsam trees. It shall be, when you hear the sound of marching in the tops of the balsam trees, then you shall act promptly, for then the LORD will have gone out before you to strike the army of the Philistines.” Then David did so, just as the LORD had commanded him, and struck down the Philistines from Geba as far as Gezer.