1 Samuel 17:15

But David went, and returned from Saul,.... Or "from above Saul"; Josephus u says, the physicians of Saul advised to get a man to stand υπερ κεφαλνς, "over his head", and sing psalms and hymns to him; and Saul being recovered from his frenzy and melancholy, by means of David's music, he was dismissed from him, or had leave to go home, or he returned upon Saul's taking the field; though one would think, if he was now his armourbearer, he would have gone with him, see 1 Samuel 16:21. It seems that when he was called to the court of Saul, that he did not continue there, but was going and coming, was there at certain times when Saul wanted him; and so when in the camp he might go and return as there was occasion for it:

to feed his father's sheep at Bethlehem; for though he was anointed king, and was called to court, yet such was his humility, that he condescended to attend this employment of keeping sheep; and though Jesse knew all this, yet he kept him at home to this business, when it might be more reasonably thought he would have lain in the way of preferment, had he followed Saul to the camp, and appeared in the army; but he chose to leave things to the providence of God to work the way for him, and by which he was directed to take the following step, though perhaps without any design to his son's future promotion.

u Antiqu. l. 6. c. 8. sect. 2.