Adam Clarke on 1 Samuel 26:15

Art not thou a valiant man? - This is a strong irony. Ye are worthy to die; ye are sons of death - ye deserve death for this neglect of your king. And had not Saul been so deeply affected with David's generosity in preserving his life, he had doubtless put Abner and his chief officers to death; though they were not to blame, as their apparent neglect was the effect of a supernatural sleep.