Samuel said, How can I go? if Saul hear it, he will kill me. Yahweh said, Take a heifer with you, and say, I am come to sacrifice to Yahweh.
Actually, David had a great admiration for Saul. Of course just a young boy, and he was at that hero age, and Saul, big, tall, handsome fellow became sort of a hero in David's eyes. David always respected Saul right to his death and even after his death. David never lost his respect for this man.