Isaiah 4:3-4. “And it shall come to pass, that he that is left in Zion and he that remaineth in Jerusalem shall be called holy, even every one that is written among the living in Jerusalem: When the Lord shall have washed away the filth of the daughters of Zion, and shall have purged the blood of Jerusalem from the midst thereof by the spirit of burning.
(This is Jerusalem today as seen from the Mount of Olives)
When God comes in all His wrath and splendor to deliver the remnant in Israel from their enemies, that remnant will finally turn to God. God will fulfill Is. 1:18, to “wash you, make you clean” that the people themselves failed to fulfill. He will do so by the spirit (or blast) of judgment, and by the spirit of burning.
Fire cleanses. Judgment restores. This baptism of fire is foretold by John the Baptist in Matthew 3:11. Israel will finally come into her own right relationship with God, and the promises of her greatness and restoration will be fulfilled.