1 Chronicles 10:13
So Saul died for his transgression which he committed against the LORD, even against the word of the LORD, which he kept not, and also for asking counsel of one that had a familiar spirit, to enquire of it;
So Saul died for his transgression,....
See Gill on "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.