Charles Ellicott Commentary 1 Kings 14:9

"but hast done evil above all that were before thee, and hast gone and made thee other gods, and molten images, to provoke me to anger, and hast cast me behind thy back:" — 1 Kings 14:9 (ASV)

But hast done evil above all that were before thee. —The language is strong, considering the many instances of false god worship in the days of the Judges and the recent apostasy of Solomon—not to mention the idolatry of the golden calf in the wilderness, and the establishment of idolatrous sanctuaries in former times at Ophrah and Dan (Judges 8:27; Judges 18:30–31). Indeed, the guilt of Jeroboam’s act was intensified by his presumptuous contempt for God's special promise, given on the sole condition of obedience.

In this respect, perhaps, he is said below—in an expression seldom used elsewhere—to have “cast God Himself behind his back.” But the reference is probably mainly to the unprecedented effect of the sin, coming at a critical point in Israel's history, and from that time onward poisoning the wellsprings of national faith and worship. Other idolatries came and went, but this one continued and at all times made Israel to sin.

Other gods and molten images. —See in 1 Kings 11:28 the repetition of the older declaration in the wilderness, These be thy gods, O Israel. Jeroboam would have justified using the calves as mere emblems of the true God. However, Ahijah rejects this plea, maintaining that these molten images, expressly forbidden in the Law, were truly objects of worship—other gods,—as all experience indeed shows that such forbidden emblems eventually tend to become. Moreover, 1 Kings 14:15 indicates that the vile worship of the Asherah (“groves”) became associated with Jeroboam’s idolatry.