And from that day Saul kept David with him and did not let him return to his father’s house.
David was anointed to the crown to take it out of Saul's hand, and over Jonathan's head, and yet here we find, I. That Saul, who was now in possession of the crown, reposed a confidence in him, God so ordering it, that he might by his preferment at court be prepared for future service.
Commenting on 1 Samuel 18:1-5
And Saul took him that day,.... Not only into his favour, and into his service, but into his court; even on that very day he slew the Philistine, or however as soon as it could be done: and would let him go no more home to his father's house; as he used to do before; when he only served as a musician to him, then...
Saul would let him go no more home--He was established as a permanent resident at court.