1 Chronicles 14:13-15

13Once more the Philistines raided the valley; 14so David inquired of God again, and God answered him, “Do not go directly after them, but circle around them and attack them in front of the poplar trees. 15As soon as you hear the sound of marching in the tops of the poplar trees, move out to battle, because that will mean God has gone out in front of you to strike the Philistine army.”