3:18-21 There shall be abundant Divine influences, and the gospel will spread speedily into the remotest corners of the earth. These events are predicted under significant emblems; there is a day coming, when every thing amiss shall be amended. The fountain of this plenty is in the house of God, whence the streams take rise. Christ is this Fountain; his sufferings, merit, and grace, cleanse, refresh, and make fruitful. Gospel grace, flowing from Christ, shall reach to the Gentile world, to the most remote regions, and make them abound in fruits of righteousness; and from the house of the Lord above, from his heavenly temple, flows all the good we daily taste, and hope to enjoy eternally.

21. cleanse … blood … not cleansed—I will purge away from Judah the extreme guilt (represented by "blood," the shedding of which was the climax of her sin, Isa 1:15) which was for long not purged away, but visited with judgments (Isa 4:4). Messiah saves from guilt, in order to save from punishment (Mt 1:21).