The meaning is “Rebellion is as bad as the sin of divination, and stubbornness is as bad as worshipping false gods (iniquity), and teraphim (idolatry).”
Related Commentaries of 1 Samuel 15:23
1 Samuel 15:23
23 For rebellion is as the sin of witchcraft,b and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the LORD, he hath also rejected thee from being king.