Jamieson, Fausset and Brown on Isaiah 10:20-22

20-22. The effect on the "remnant" (contrasted with the Assyrian remnant, Is 10:19); namely, those who shall be left after the invasion of Sennacherib, will be a return from dependence on external idolatrous nations, as Assyria and Egypt (2Ki 18:21; 16:7-9), to the God of the theocracy; fulfilled in part in the pious Hezekiah's days; but from the future aspect under which Paul, in Ro 9:27, 28 (compare "short work" with "whole work," Is 10:12, here), regards the whole prophecy, the "remnant," "who stay upon the Lord," probably will receive their fullest realization in the portion of Jews left after that Antichrist shall have been overthrown, who shall "return" unto the Lord (Is 6:13; 7:3; Zec 12:9, 10; 14:2, 3; Zep 3:12).