cleanse . . . cleansed = clear . . . cleared. This could be done only by avenging it; for God will "by no means clear the guilty" (Exo_34:7. Num_14:18); and Egypt, Edom, &c., were guilty (Joe_3:19), and are not to be cleansed", but punished for shedding Judah's blood. The Hebrew nakah is not used of cleansing, naturally or ceremonially. Not the same word as Isa_4:4. The Septuagint and Syriac render it "make inquisition for" in 2Ki_9:7; and evidently read nakam = to avenge (akin to nakah). This would be a vivid reference to Pent in Deu_32:42, Deu_32:43, the parallel event. Compare Rev_6:10, Rev_6:11.
have not = had not.
dwelleth in Zion = is about to make His dwelling in Zion. Thus ending like Ezekiel (Eze_48:35), Jehovah Shammah. Compare Joe_3:17. Psa_87:3. Rev_21:3.