2 Samuel 5:24
And let it be, when thou hearest the sound of a going in the tops of the mulberry trees, that then thou shalt bestir thyself: for then shall the LORD go out before thee, to smite the host of the Philistines. And let it be, when thou hearest the sound of a going in the tops of the mulberry trees, that then thou shalt bestir thyself: for then shall the LORD go out before thee, to smite the host of the Philistines.
The sound of movement in the tops of the mulberry trees was God's own appointed signal for Israel to act against the Philistines. David was to hold back from attacking until that sound was heard, and then to bestir himself and move promptly into action. That moment was the time to act because then the Lord Himself would go out before Israel to smite and defeat the host of the Philistines. David's victory and success therefore depended on following God's direction rather than choosing his own way.
The verse teaches God's people to watch attentively for the movements and signs of His providence and to expect help from heaven to work at the appointed time. That watchfulness is looking for light and refreshing to come from the Lord's presence.