Charles Ellicott Commentary 1 Samuel 18:8

"And Saul was very wroth, and this saying displeased him; and he said, They have ascribed unto David ten thousands, and to me they have ascribed but thousands: and what can he have more but the kingdom?" — 1 Samuel 18:8 (ASV)

What can he have more but the kingdom? —In this foreboding utterance of Saul, there was involved not only a conjecture which the result confirmed, but a deep inward truth: if the king stood powerless before the subjugators of his kingdom at so decisive a period as this, and a shepherd boy came and decided the victory, this was an additional mark of his rejection.—V. Gerlach, quoted in Keil.

Some years had passed since he first heard from the lips of his old prophet-friend the Divine sentence of his rejection from the kingdom. In that sad period, he had doubtless been on the lookout for the one destined by the Invisible King to be his successor. This dread expectation of ruin and dethronement had been a powerful factor in the causes that had led to the unhingement of Saul’s mind. Was not this gifted shepherd boy—now the idol of the people—the future hope of Israel?