"For the priest's lips should keep knowledge": It was the priest's duty to study the Law and to teach it faithfully, as it is said of Aaron, in Ecclus. 45:17, "He 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."
Verse 9
"have been partial in the law": in the observance of it, attending to the lesser, and taking no notice of the weightier matters of it, as the Jews are charged by Christ, and in the interpretation of it, restraining its sense only to outward actions, for which they are reproved, or "received faces", or "accepted persons in the law"; in matters of the law they were concerned in, they had respect to the persons of men, by giving the sense of it, and pronouncing judgment, in favour of some, to the prejudice of others, wrongly.
Verse 16
"He hateth putting away": This is another reason against divorce: God hates it. It is contrary to his original institution, and was only allowed for the hardness of men's hearts. Septuagint, "If thou hate her and dismiss her," etc.; Vulgate, "If thou hate her, put her away," which seems to encourage divorce, whereas in the context divorce is strongly condemned. Hence Jerome considers these words to be spoken by the Jews, quoting in their defence Moses' precept. Others think that they are ironical - Put her away, if you please; but you must bear the consequences.
"One covereth violence with his garment": or, "and violence covereth his garment," or, it might be, in the same sense, "he covereth his garment with violence", so that it cannot be hid, nor washed away, nor removed, but envelopes him and his garment; and that, to his shame and punishment. It was, as it were, "an outer garment of violence", as Asaph says in Psalm 73:6, "violence covereth them as a garment;" or David in Psalm 109:18, "he clothed himself with cursing as with a garment." It was like a garment with "fretting leprosy," unclean and making unclean, to be burned with fire. Leviticus 13:47-58. Contrariwise, the redeemed saints had Revelation 7:14 "washed their robes and made them white in the Blood of the Lamb." Having declared God's hatred of this their doing, he sums up in the same words, but more briefly; "and this being so, ye shall take heed to your spirit, and not deal treacherously." Maurer translates, "And covereth his garment with injury." The Hebrew favors "garment," being accusative of the thing covered. Their "violence" is the putting away of their wives; the "garment" with which they try to cover it is the plea of Moses' permission.