2 Samuel 17-25
When the Philistines heard that they had anointed David king over Israel, all the Philistines went up to seek out David; and when David heard of it, he went down to the stronghold. Now the Philistines came and spread themselves out in the valley of Rephaim. Then David inquired of the Lord, saying, “Shall I go up against the Philistines? Will You give them into my hand?” And the Lord said to David, “Go up, for I will certainly give the Philistines into your hand.” So David came to Baal-perazim and defeated them there; and he said, “The Lord has broken through my enemies before me like the breakthrough of waters.” Therefore he named that place Baal-perazim. They abandoned their idols there, so David and his men carried them away.
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.