1 Samuel 26:16
This thing is not good that thou hast done. As the LORD liveth, ye are worthy to die, because ye have not kept your master, the LORD’s anointed. And now see where the king’s spear is, and the cruse of water that was at his bolster. This thing is not good that thou hast done. As the LORD liveth, ye are worthy to die, because ye have not kept your master, the LORD’s anointed. And now see where the king’s spear is, and the cruse of water that was at his bolster.
This chapter falls after Saul killed the priests of the Lord, when Abiathar son of Ahimelech escaped and fled to David and David sheltered him because Saul sought both David's life and Abiathar's life. David spoke from a hilltop at a safe distance from Saul's sleeping camp, crying out with a loud voice to Abner and the people in the hearing of the king and the people of Israel. The utterance is a cutting rebuke to Abner, addressed as a valiant man with none like him in Israel, for not guarding his lord the king when one of the people came in to destroy him, declaring that failure not good and worthy of death for him and those with him because Saul was his master, the Lord's anointed.
By pointing to the king's spear and the cruse of water that had been at his bolster and had been taken as he slept, David proved that Saul's life had been in his power and was spared. The rebuke is a second demonstration of David's respect for his sovereign's life, which astonished and subdued Saul and brought from him a still deeper and more humble acknowledgment of his fault. The reproof rankled in Abner's breast and drove him to carry out a revengeful purpose to create division in Israel whereby he himself might be exalted.