And it came to pass afterward, that David's heart troubled him, because he had cut off Saul's robe.
All Commentaries on 1 Samuel 24:5 Go To 1 Samuel 24
Augustine of Hippo
AD 430
In the same way, Saul’s kingdom foreshadowed one that should last forever, though he personally was reprobate and rejected. The very oil with which he was anointed (the chrism by token of which he was called a “Christ”) must be understood symbolically as pointing to a profound mystery. David himself so religiously respected this anointed state that he was conscience-stricken when, in a dark cave where Saul had entered to ease himself, David came up, unseen, from behind and cut off a tiny piece of Saul’s robe. David did this merely to have evidence later how he had spared Saul when he could have killed him, thus hoping to disabuse Saul of the idea which drove him implacably to pursue David as his foe. Nevertheless, David quaked with fear that perhaps merely by so touching Saul’s garments he was guilty of sacrilege.… Such deep religious reverence was paid to this foreshadowing figure, not for what it was in itself but precisely because of the reality it typified.