And he shall sit [as] a refiner, and purifier of silver,.... Kimchi interprets this, as he does the latter part of the preceding verse Mal 3:2, of the day, and not of the Lord, which he compares to a judge that sits and separates the guilty from the innocent; see 1Co 3:13 but it is to be understood of the Lord himself, and expresses his diligence in sitting and separating good men and principles from bad ones, just as silver is purified and refined from dross.
Maimonides understands the passage of the Messiah; for he says,"in the days of the King Messiah, when his kingdom is restored, and all Israel shall be gathered to him, all will have their genealogies set right by his mouth, through the Holy Spirit that rests upon him, as it is said, "he shall sit a refiner and purifier":''as a refiner sits and observes his metal while it is melting, and waits the proper time to pour it out and separate the dross from it; so Christ is here represented as sitting, while his people are purifying and refining by the various ways and means he makes use of: it denotes the continued care of Christ over them; his eye is upon them, that nothing be lost but their dross and corruption; and his patience in waiting to be gracious to them, and do them good; and his diligent attention to the proper season of doing it; designing by all that he does, not their hurt and damage, but their real good, for he saves them, though it be by fire; and indeed every trial and affliction is for the purifying of their souls, and the brightening of their graces, and increasing their spiritual experience, light, and knowledge.
And he shall purify the sons of Levi; the priests, either literally understood, some of these were converted from their evil principles and practices, and became obedient to the doctrines of the Gospel, Ac 6:7 or figuratively, the apostles of Christ and ministers of the Gospel, who were made clean by him; or rather all the people of God, who are made priests as well as kings, and are a royal priesthood, and are purified by Christ, both by his blood, and the imputation of his righteousness, by which they become without spot and blemish, and as white as snow; and by the Spirit in sanctification, he sprinkling clean water upon them, and purifying their hearts by faith in the blood of Jesus; and also by afflictive dispensations of Providence sanctified unto them.
Mention is made of the priests and Levites, because these were so very corrupt in the times of Christ, and as appears from the preceding chapters.And purge them as gold and silver; are purged in the fire from their dross: this shows of what worth and value, and in what esteem the Lord's people are to him; he reckons of them as gold and silver, and as his peculiar treasure: and it suggests, that before conversion they are joined unto and mixed with wicked men, comparable to dross; and that they have in them the dross, corruption, and impurity of sin; which is original and natural to them, and inherent in them, and which can only be removed by the grace of God and blood of Christ.
That they may offer unto the Lord an offering in righteousness; themselves, their bodies and souls; the sacrifices of prayer, praise, and alms deeds; to the offering up of which in righteousness, in sincerity and truth, in an upright way, it is necessary that a person should be purified by the blood of Christ, and sanctified by the grace of his Spirit.
Hilchot Melachim, c. 12. sect.