4 Bible Verses about Apostasy Of Saul

Samuel said to Saul, "I will not return with you; for you have rejected the word of Yahweh, and Yahweh has rejected you from being king over Israel." As Samuel turned about to go away, Saul grabbed the skirt of his robe, and it tore. Samuel said to him, "Yahweh has torn the kingdom of Israel from you this day, and has given it to a neighbor of yours who is better than you.read more.
Also the Strength of Israel will not lie nor repent; for he is not a man, that he should repent."

Saul was afraid of David, because Yahweh was with him, and was departed from Saul.

Samuel said to Saul, "Why have you disturbed me, to bring me up?" Saul answered, "I am very distressed; for the Philistines make war against me, and God has departed from me, and answers me no more, neither by prophets, nor by dreams. Therefore I have called you, that you may make known to me what I shall do."

Because you didn't obey the voice of Yahweh, and didn't execute his fierce wrath on Amalek, therefore Yahweh has done this thing to you this day.