Priests: Services of Teaching the Law
Source: TTT
Deuteronomy 33:8, 10
Concerning Levi he said: “Give Your Thummim to Levi and Your Urim to Your godly one, whom You tested at Massah and contested at the waters of Meribah. / He will teach Your ordinances to Jacob and Your law to Israel; he will set incense before You and whole burnt offerings on Your altar.
Malachi 2:7
For the lips of a priest should preserve knowledge, and people should seek instruction from his mouth, because he is the messenger of the LORD of Hosts.