III. That God will reform his church and will rectify and amend whatever is amiss in it, v. 4. Then the remnant shall be called holy, when the Lord shall have washed away their filth, washed it from among them by cutting off the wicked persons, washed it from within them by purging out the wicked thing. They shall not be called so till they are in some measure made so. Gospel times are times of reformation (Heb. ix. 10), typified by the reformation in the days of Hezekiah and that after captivity, to which this promise refers. Observe, 1. The places and persons to be reformed. Jerusalem, though the holy city, needed reformation; and, being the holy city, the reformation of that would have a good influence upon the whole kingdom. The daughters of Zion also must be reformed, the women in a particular manner, whom he had reproved, ch. iii. 16. When they were decked in their ornaments they thought themselves wondrously clean; but, being proud of them, the prophet call them their filth, for no sin is more abominable to God than pride. Or by the daughters of Zion may be meant the country towns and villages, which were related to Jerusalem as the mother-city, and which needed reformation. 2. The reformation itself. The filth shall be washed away; for wickedness is filthiness, particularly blood-shed, for which Jerusalem was infamous (2 Kings xxi. 16), and which defiles the land more than any other sin. Note, The reforming of a city is the cleansing of it. When vicious customs and fashions are suppressed, and the open practice of wickedness is restrained, the place is made clean and sweet which before was a dunghill; and this is not only for its credit and reputation among strangers, but for the comfort and health of the inhabitants themselves. 3. The author of the reformation: The Lord shall do it. Reformation-work is God's work; if any thing be done to purpose in it, it is his doing. But how? By the judgment of his providence the sinners were destroyed and consumed; but it is by the Spirit of his grace that they are reformed and converted. This is the work that is done, not by might, nor by power, but by the Spirit of the Lord of hosts (Zech. iv. 6), working both upon the sinners themselves that are to be reformed and upon magistrates, ministers, and others that are to be employed as instruments of reformation. The Spirit herein acts, (1.) As a spirit of judgment, enlightening the mind, convincing the conscience,—as a spirit of wisdom, guiding us to deal prudently, (Isa. lii. 13),—as a discerning, distinguishing, Spirit, separating between the precious and the vile. (2.) As a Spirit of burning, quickening and invigorating the afflictions, and making men zealously affected in a good work. The Spirit works as fire, Matt. iii. 11. An ardent love to Christ and souls, and a flaming zeal against sin, will carry men on with resolution in their endeavours to turn away ungodliness from Jacob. See Isa. xxxii. 15, 16.