Saul's paranoia was so severe that his own people could see it. He accused the priests of conspiring with David against him and ordered them killed. The Israelites would not do it, so it fell to an Edomite. David had to constantly stay on the move in southern Judah to avoid being trapped and killed by Saul. Yet for all that, when presented with the opportunity to kill Saul as he was relieving himself in a cave, David did not raise his hand against the Lord's anointed. If he could stay alive, that decision would pay dividends when David united the nation after Saul's death.
