Midrash su I Re 13:6

And the king answered and said unto the man of God: “Entreat now the favor of the Lord thy God, and pray for me” (ibid., v. 6). Two amoraim¹³Talmudic authorities who lived after the final redaction of the Mishnah. discussed this verse. One commented that he said thy God and not “my God.” The other retorted: How could he call Him “my God” while he stood and sacrificed before an idol whom he addressed as “my god”? Nevertheless The man of God entreated the Lord, and the king’s hand was restored, and became as it was before (ibid.). What is meant by as it was before? R. Judah the son of Simon began the discussion with the verse in the name of R. Joshua the son of Levi: Though thou brayest a fool in mortar with a pestle among groats, yet will not his foolishness depart from him (Prov. 27:22). That is to say, it will have no effect (on the fool, he learns nothing). Likewise he had previously sacrificed to an idol, and he did so again.