Isaiah 27:9
By this therefore shall the iniquity of Jacob be purged; and this is all the fruit to take away his sin; when he maketh all the stones of the altar as chalkstones that are beaten in sunder, the groves and images shall not stand up. By this therefore shall the iniquity of Jacob be purged; and this is all the fruit to take away his sin; when he maketh all the stones of the altar as chalkstones that are beaten in sunder, the groves and images shall not stand up.
Oppression by Assyria and the experience of captivity were appointed as chastisement for Judah, and by this discipline the iniquity of Jacob would be purged and his sin taken away. The affliction was not merely punitive but cleansing, accomplishing the removal of sin through the humbling effect of bondage. When that purging work had been done, the way would be opened for restoration.
After the captivity, those who remained faithful and all who chose to serve God would be permitted to return to their ancestral land. The return was conditioned on loyalty and willing service, gathering the obedient back to the inheritance from which they had been removed.