Not only because it was injurious, and reproachful, and dangerous to the king; but possibly because he had some secret thought of doing more to him, though he suppressed and overcame it; for he attempted this in pursuance of his soldiers suggestion, 1 Samuel 24:4 which if followed would have carried him to further action.
Related Commentaries of 1 Samuel 24:5
1 Samuel 24:5
5 And it came to pass afterward, that David's heart smote him, because he had cut off Saul's skirt.