What is the consequence of that all of you are Sigim?
Radak: Since you should have been Kesef, and you were Sigim, I will gather you and melt you in the fire of My anger (19-21). Just like something melted loses its initial form, and all the more so mixed metals lose their form when they are melted, so they will perish via sword, hunger and plague. Even though those who remain will be lost ? they were in their land for good, and they will be exiled from it for evil.
Malbim: Therefore, He gathered them to send them to Galus. Via this, He selected the good among the; they had a remnant in Galus. "Hir'ani Hashem v'Hinei Shnei Duda'ei Se'enim" (Yirmeyah 24:1). It explains there that Galus Yechanyah were like good figs senmt to Bavel for the good, and for a remnant. He separated them from the bad figs that remained [in Yerushalayim] for a curse.
What is the significance of gathering them to Yerushalayim?
Radak: This will be like the furnace for metals.
