In that day; i.e. "at that time"—the time of the destruction of Assyria. The remnant of Israel (see Isaiah 1:9). Isaiah had indicated his firm belief in the existence of this faithful remnant and its return, in the name which he had given to his son, Shear-Jashub (see note on Isaiah 7:3).
The escaped. Those who escape from the destruction to be caused by the Assyrian invasion. Shall no more again stay upon him that smote them. We are told in the Second Book of Chronicles (Isaiah 28:23) that Abaz "sacrificed to the gods of Damascus which smote him"—and we know that he also trusted to Tiglath-Pileser, who "distressed him and strengthened him not" (2 Chronicles 28:21).
Among the "remnant" there shall be no such mistaken confidences. But shall stay upon the Lord; i.e. "shall put their trust in God; and him only".