Here is a conversation that God had with priests who became lax in their duties and beliefs. This had happened after they were restored to Israel from the captivity in Babylon, yet they offered imperfect sacrifices and did not keep in full the law of Moses. The message was so tough and so necessary that the prophet who delivered it used a pseudonym.
Malachia 3: 13-23
You have defied me in word, says the Lord, yet you ask, “What have we spoken against you?” You have said, “It is vain to serve God, and what do we profit by keeping his command, and going about in penitential dress in awe of the Lord of hosts? Rather must we call the proud blessed; for indeed evildoers proper, and even tempt God with impunity.” Then they who fear the Lord spoke with one another, and the Lord listened attentively; and a record book was written before him of those who fear the Lord and trust in his name. And they shall be mine, says the Lord of hosts, my own special possession, on the day I take action. And I will have compassion on them, as a man has compassion on his son who serves him. Then you will see the distinction between the just and the wicked; between him who serves God, and him who does not serve him. For lo, the day is coming, blazing like an oven, when all the proud and all evildoers will be stubble, and the day that is coming will set them on fire, leaving them neither root nor branch, says the Lord of hosts. But for you who fear my name, there will arise the sun of justice with its healing rays; and you will gambol like calves out of the stall and tread down the wicked; they will become ashes under the soles of your feet, on the day I take action, says the Lord of hosts.
Remember the law of Moses my servant, which I enjoined upon him on Horeb, the statutes and the ordinances for all Israel.
Lo, I will send you Elijah, the prophet, before the day of the Lord comes, the great and terrible day, to turn the hearts of the fathers to their children, and the hearts of the children to their fathers, lest I come and strike the land with doom.