Isaiah 66:19
And I will set a sign among them, and I will send those that escape of them unto the nations, to Tarshish, Pul, and Lud, that draw the bow, to Tubal, and Javan, to the isles afar off, that have not heard my fame, neither have seen my glory; and they shall declare my glory among the Gentiles.
Those sent are surviving witnesses from among God's people who escape judgment. They are sent to distant Gentile nations and far-off islands that have not heard of God nor seen His glory, to Tarshish, Pul and Lud that draw the bow, to Tubal and Javan, to the isles afar off. Their work is to declare God's glory among the Gentiles by carrying to the world the good news of salvation and peace and the knowledge of God's truth.
The scattering of Israel among heathen lands served this missionary purpose of carrying knowledge of God to the world. The verse is literally fulfilled when bearers of salvation go to the ends of the earth to every kindred and people.
Those sent bring converts from all nations as an offering to the Lord at His holy mountain Jerusalem. From among those Gentile converts some are taken for priests and for Levites. If God's people are loyal, true and submissive, He will bring them back to their own land.