Those forementioned excellent priests did so teach, and so live, forasmuch as they did well consider it was their duty to be well acquainted with, and to have a great insight into, the law of God. The priest's lips should keep knowledge; it is that their office binds them to; it is the duty of all God's people to know his law, but the priest's duty to know it more than others, Leviticus 10:11, for they were to teach Israel, Deuteronomy 33:10. And they, the people of Israel, should seek the law at his mouth; in difficult cases, in controversies, &c., the people were to consult and advise with the priests, and inquire what the law said in the case. For he is the messenger, interpreter, ambassador, or legate, of the Lord of hosts with the people, lieger among them, and who therefore ought to be advised with about his Lord's mind.
Related Commentaries of Malachi 2:7
Malachi 2:7
7 For the priest's lips should keep knowledge, and they should seek the law at his mouth: for he is the messenger of the LORD of hosts.