John Gill Bible Commentary

And let it be, when thou hearest the sound of a going in the tops of the mulberry trees,.... Of a going of the wind on the tops of these trees, making a rustling upon them, and that in such a manner as to resemble the going of men, or march of armies, as if they were moving in the air over the tops of the mulberry trees; which Jarchi and R. Isaiah interpret of angels being sent of God, and moving at that time to help David, and destroy the Philistines; so the Targum on Ch1 14:15. These trees being in Judea account for silk there, Eze 16:10; though some think time was not known so early; others suppose it was, and to be the Hebrew byssus mentioned by Pausanias (a), as being of a yellow colour: that then thou shall bestir thyself; or move towards the camp of the Philistines, and fall upon them in the rear, who, by reason of the sound in the trees, would not hear the motion of the Israelites; or, if they heard it, would take it to be no other than the motion of the trees they heard, both sounds being confounded together; or they would take the sound they heard for the motion of the enemy in the front, and give way, and so fall into the hands of the Israelites in their rear, which must throw them into the utmost confusion and consternation: for then shall the Lord go out before thee to smite the host of the Philistines: by an angel or angels; so the Targum,"for then shall go forth the angel of the Lord, to make thee prosperous to slay in the camp of the Philistines;'' that being the precise time for the salvation of Israel, and the destruction of the Philistines, and the token of it. (a) Eliac. sive, l. 5. p. 294.