1 Kings 11:4

Was old — As having now reigned nigh thirty years. When it might have been expected that experience would have made him wiser: then God permitted him to fall so shamefully, that he might be to all succeeding generations an example of the folly, and weakness of the wisest and the best men, when left to themselves. Turned his heart — Not that they changed his mind about the true God, and idols, which is not credible; but they obtained from him a publick indulgence for their worship, and possibly persuaded him to join with them in the outward act of idol — worship; or, at least, in their feasts upon their sacrifices, which was a participation of their idolatry.