Said in his heart, i.e. reasoned within himself: The phrase discovers the fountain of his error, that he did not consult with God, who had given him the kingdom; as in all reason, and justice, and gratitude he should have done; nor believed God's promise, 1 Kings 11:38; but his own imaginations and carnal policies.
Related Commentaries of 1 Kings 12:26
1 Kings 12:26
26 And Jeroboam said in his heart, Now shall the kingdom return to the house of David: