Malachi 2:7

For the priest's lips should keep knowledge - o "He assigns the reason for what he had just said, the law of truth was in his mouth; they had done what it was their duty to do; as in Ecclesiasticus it is said of Aaron (Ecclesiasticus 45:17), 'God gave unto him His commandments, and authority in the statutes of judgments, that he should teach Jacob the testimonies, and inform Israel in His laws.' So Paul requires of Titus to ordain such overseers, as shall be able to Titus 1:9, 'exhort by sound doctrine and to convince gainsayers.' Wherefore Ambrose calls the Bible, which contains the law of God, 'the book of priests,' as specially belonging to them, to be specially studied by them. Jerome notes that he says keep, not 'give forth,' that they should speak seasonably, and give their fellow-servants meat in due season."

For he is the messenger (or angel) of the Lord of hosts - Malachi gives to the priest the title which belongs to the lowest order of the heavenly spirits, as having an office akin to theirs; as Haggai does to the prophet, Haggai 2:11. as an extraordinary "messenger" of God; and Paul tells the Galatians Gal 4:14, "ye received me as an angel of God, as Christ Jesus;" and Christ, by John, speaks to the leaders of the seven congregations, good or bad, or of mixed good and bad, as "the angels Revelation 1:20 of those churches."

"Since in the heavenly hierarchy the order of angels is the lowest, and in the eucharistical hierarchy the order of the priesthood is the highest" , "most truly is the priest of God called angel, i. e., messenger, because he intervenes between God and man, and announces the things of God to the people; and, therefore, were the Urim and Thummim placed on the priest's breastplate of judgment, that we might learn, that the priest ought to be learned, a herald of divine truth." Much more in the New Testament. "Who, as it were in a day, can form one of earth, to be the defender of truth, to stand with angels, to give glory with archangels, to transmit the sacrifices to the altar above, to be partaker of the priesthood of Christ, to reform the thing formed, and present the image, to re-create for the world above, to be a god and make men partakers of the divine nature?" 2 Peter 1:4. "The priesthood is enacted on earth, but is ranked with the heavenly ranks. Very rightly. For not man, not angel, not archangel, not any other created power, but the Paraclete Himself hath ordained this office, and persuaded them, while yet abiding in the flesh, to conceive the ministry of the angels. Wherefore, he who is consecrated as priest, ought to be pure, as if he stood among the heavenly powers." , "The throne of the priesthood is placed in the heavens, and he is entrusted with ministering things of heaven. Who saith this? The King of heaven Himself. For He saith, 'Whatsoever ye shall bind on earth, shall be bound in heaven, and whatsoever ye shall loose on earth, shall be loosed in heaven.' So the priest standeth in the middle between God and human nature, bringing down to us divine benefits, and transmitting thither our supplications."

2:7 Should keep knowledge - It is this 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. And they - The people.