Malachi 2:7

What the Prophet has said of the first priests he extends now to the whole Levitical tribe, and shows that it was a perpetual and unchangeable law as to the priesthood. He had said that Levi had been set over the Church, not to apply to himself the honor due to God, but to stand in his own place as the minister of God, and the teacher of the chosen people. The same thing he now confirms, declaring it as a general truth that the lips of the priest ought to retain knowledge, as though he had said, that they were to be the store-house from which the food of the Church was to be drawn. God then did appoint the priests over his chosen people, that the people might seek their food from them as from a store-room, according to what we find to be the case with a master of a family, who has his store of wine and his store of provisions. As then the food of a whole family is usually drawn out from places where provisions are laid up, so the Prophet makes use of this similitude, — that God has deposited knowledge with the priests, so that the mouth of every priest might be a kind of store-house, so to speak, from which the people are to seek knowledge and the rule of a religious life: Keep knowledge then shall the lips of the priest, and the law shall they seek from his mouth (220)

He shows how it is to be kept; the priests are not to withhold it, but the whole Church is to enjoy the knowledge of which they are the keepers. They shall then seek or demand the law from his mouth.

Law may be taken simply for truth; but the Prophet no doubt alludes here to the doctrine of Moses, the only true fountain of all knowledge. We indeed know that God included in his law whatever was necessary for the welfare of his Church; nor was there anything added by the Prophets. Our Prophet then so includes every truth in the word, תורה, ture, law, that he might at the same time show that it was laid up in what Moses has taught.

He says in the last place, that the priest is the messenger of Jehovah. He briefly defines here what the priesthood is, even an embassy which God commits to men, that they may be his interpreters in teaching and ruling the Church. What then is a priest? A messenger of God, and his interpreter. It hence follows that the office of teaching cannot be separated from the priesthood; for it is a monstrous thing when any one boasts himself to be a priest, when he is no teacher. The Prophet then draws an argument from the definition itself, when he says that a priest is a messenger of God. Then follows the contrast when he says

A son should honor a father,
And a servant, his Lord.

This use of the future, as designating a duty or obligation, is much more frequent in Hebrew than what is commonly supposed. — Ed.