He will turn, i.e. he will alter his course and the manner of his dealing with you, and will be as severe as ever he was kind and gracious. Consume you, after that he hath done you good; he will repent of all his former kindness, and his goodness abused will be turned into fury.
Related Commentaries of Joshua 24:20
Joshua 24:20
20 If ye forsake the LORD, and serve strange gods, then he will turn and do you hurt, and consume you, after that he hath done you good.