1. Purity. This is put last here, as a reason for the rest (v. 21); but we may consider it first, as the ground and foundation of the rest: I will cleanse their blood that I have not cleansed, that is, their bloody heinous sins, especially shedding innocent blood; that filth and guilt they had contracted by sin, which rendered them unfit for communion with God, and made them odious to his holiness and obnoxious to his justice; this they shall be washed from in the fountain opened, Zech. xiii. 1. That shall be cleansed by the blood of Christ which could not be cleansed by the sacrifices and purifications of the ceremonial law. Or, if we apply it to the happiness of a future state, it intimates the cleansing of the saints from all these corruptions from which they were not cleansed either by ordinances or providences in the world; there shall not be the least remains of sin in them there. Here, though they are washing daily, there is still something that is not cleansed; but in heaven, even that also shall be done away. And the reason is because the Lord dwells in Zion, dwells with his church, and much more gloriously with that in heaven, and holiness becomes his house for ever, for which reason, where he dwells there must be, there shall be, a perfection of holiness. Note, Though the refining and reforming of the church is work that goes on slowly, and still there is something we complain of that is not cleansed, yet there is a day coming when every thing that is amiss shall be amended, and the church shall be all fair, and no spot, no stain in her; and we must wait for that day.