The spear. — The spear was Saul’s especial sign of royalty. “This taking away of the spear from Saul’s head as he slept was an omen of the transfer of his royalty to David.” — Bishop Patrick, quoted by Wordsworth.
And the cruse of water. — “A very ancient usage explains why the cruse of water is here brought into such special prominence. According to this custom, some high dignitary always had in keeping a costly ewer for the king’s necessary ablutions, and it was specially his duty to take it with him, and present it to the king during campaigns or other journeys, so that its disappearance would involve almost as great a disgrace to the king as the loss of his sceptre” (Ewald, in reference to Psalms 60:8, states his belief that this custom existed in the time of David). — Ewald, History of Israel, “David,” ii. 3 (Note). The same scholar also writes that “there are many other instances of similar stories, in which the future conqueror and founder of a new dynasty is represented as having received at first some symbol of royalty from his predecessors by accident, as it were, or in sport. Thus Alexander at first takes the royal divining cup from Dârâ as if in sport: a story which in the Shâhnâmeh no longer appears in its original light; and in nothing was the belief in omens so strong as in the high affairs of state.” — “David,” ii. 3 (Note).