Isaiah 66: 18-19.
18 For I know their works and their thoughts: it shall come, that I will gather all nations and tongues; and they shall come, and see My glory.
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.
This last part of Isaiah is devoted to the Millennium (vv. 18-21) and the new heavens and the new earth (vv. 22-24).
First, God speaks of gathering all nations to see His glory, of setting up a sign among them by sending Jewish missionaries to those who have not heard of His fame, or seen His glory. He speaks of the nations bringing the Israelites back to Jerusalem.
The sign or standard will be placed in Israel as a rallying place for all the Gentiles as well as Israelites.
Those that escape refers to the Jews that escaped the terrible tribulation judgments and the efforts of the Gentiles to exterminate them during the last days. These Jews will be sent as Missionaries during the Millennium. They will go to all nations and declare the fame and glory of God.