Malachi 2:8
But ye are departed out of the way; ye have caused many to stumble at the law; ye have corrupted the covenant of Levi, saith the LORD of hosts. But ye are departed out of the way; ye have caused many to stumble at the law; ye have corrupted the covenant of Levi, saith the LORD of hosts.
Malachi 2:8 is spoken to the priests who were entrusted with teaching God's law. Those priests had departed out of God's way by failing to keep His ways. Their departure included showing partiality in applying the law.
That partiality meant being strict where obedience suited them while disregarding requirements that touched their personal interests and earthly treasures. They caused many to stumble at the law. They did this by their teaching, conduct, and bad example, which shows that a minister's example can lead others away from obedience to God's law.
By these actions they corrupted and violated the covenant God had made with Levi. In doing so they dishonored the Lord. Their failure to keep God's ways and their partiality brought them into contempt.
Their failure stands in contrast with the faithful priestly duty to preserve knowledge of the law. It also stands in contrast with the faithful priest whose teaching turns many from iniquity.