1 Chronicles 10:13

So Saul died for his transgression,....

1 Samuel 31:13 A violent and dishonourable death, which was suffered on account of the sins he was guilty of:

one was, which he committed against the Lord, even against the word of the Lord, which he kept not; both in not staying for Samuel the time appointed, and by sparing the Amalekites whom he was bid to destroy, 1 Samuel 13:13

and also for asking counsel of one that had a familiar spirit, to inquire of it; what he should do with respect to engaging in battle with the Philistines, 1 Samuel 28:8 which to do was contrary to an express command of God, Leviticus 19:31.