Charles Ellicott Commentary 1 Chronicles 10:13-14

"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], and inquired not of Jehovah: therefore he slew him, and turned the kingdom unto David the son of Jesse." — 1 Chronicles 10:13-14 (ASV)

A concluding reflection from the mind of the chronicler himself. He sums up his account concerning the ruin of Saul by assigning its moral basis, namely, Saul’s “unfaithfulness by which he showed himself unfaithful to Jehovah.” The same charge was made against the Transjordan tribes in 1 Chronicles 5:25, and against the people of Judah in 1 Chronicles 9:1.