Charles Ellicott Commentary 1 Samuel 29:4

"But he princes of the Philistines were wroth with him; and the princes of the Philistines said unto him, Make the man return, that he may go back to his place where thou hast appointed him, and let him not go down with us to battle, lest in the battle he become an adversary to us: for wherewith should this [fellow] reconcile himself unto his lord? should it not be with the heads of these men?" — 1 Samuel 29:4 (ASV)

Go down. —This is a technical military expression, used constantly, on account of the necessity of the troops descending from the hill country in which they were encamped to the plain in order to fight.