1 Chronicles 14:15

As soon as you hear the sound of marching in the tops of the balsam trees, move out to battle, because this will mean that God has gone out before you to strike the camp of the Philistines.”

And it shall be, when thou shalt hear a sound of going in the tops of the mulberry trees, that then thou shalt go out to battle: for God is gone forth before thee to smite the host of the Philistines.