Jamieson, Fausset and Brown on 1 Samuel 18:4

4. Jonathan stripped himself of the robe that was upon him, and gave it to David--To receive any part of the dress which had been worn by a sovereign, or his eldest son and heir, is deemed, in the East, the highest honor which can be conferred on a subject (see on Es 6:8). The girdle, being connected with the sword and the bow, may be considered as being part of the military dress, and great value is attached to it in the East.

1Sa 18:5-9. Saul Envies His Praise.