Charles Ellicott Commentary 1 Chronicles 10:13

"So Saul died for his trespass which he committed against Jehovah, because of the word of Jehovah, which he kept not; and also for that he asked counsel of one that had a familiar spirit, to inquire [thereby]," — 1 Chronicles 10:13 (ASV)

Even against the word of the Lord. —Saul’s unfaithfulness was twofold: (1) he did not observe the prophetic word of Jehovah (compare 1 Samuel 13:13; 1 Samuel 15:11); and (2) he consulted a necromancer, to the neglect of consulting Jehovah (1 Samuel 28:0).

And also for asking counsel. — And also by consulting the necromancer in order to get a response. “Turn ye not to the necromancers” (Leviticus 19:31). (See also Isaiah 8:19.) Saul broke the general law of his people, as well as special commands addressed to himself. No allusion is made to his cruel slaughter of the priests (1 Samuel 22:18), nor to his implacable hatred of David.