2 Chronicles 33:13 - Joseph Benson’s Commentary on the Old and New Testaments

Then Manasseh knew that the Lord he was God He was convinced, by his own experience, of God's power, justice, and goodness; that Jehovah alone was the true God, and not those idols which he had worshipped, by which he had received great hurt and no good. He might have known this at a less expense, if he would have given due attention and credit to the word written and preached: but it was better to pay thus dear for the knowledge of God, than perish in ignorance and unbelief.