For the priest's
literally, one officiating, a priest; also (by courtesy) an acting priest (although a layman) -- chief ruler, own, priest, prince, principal officer.
the lip (as a natural boundary); by implication, language; by analogy, a margin (of a vessel, water, cloth, etc.)
to hedge about (as with thorns), i.e. guard; generally, to protect, attend to, etc.
knowledge -- cunning, (ig-)norantly, know(-ledge), (un-)awares (wittingly).
and they should seek
to search out (by any method, specifically in worship or prayer); by implication, to strive after
a precept or statute, especially the Decalogue or Pentateuch -- law.
at his mouth
the mouth (as the means of blowing), whether literal or figurative (particularly speech); specifically edge, portion or side; adverbially (with preposition) according to
for he is the messenger
a messenger; specifically, of God, i.e. an angel (also a prophet, priest or teacher) -- ambassador, angel, king, messenger.
of the LORD
(the) self-Existent or Eternal; Jehovah, Jewish national name of God -- Jehovah, the Lord.
a mass of persons (or figuratively, things), especially reg. organized for war (an army); by implication, a campaign, literally or figuratively (specifically, hardship, worship)