Charles Ellicott Commentary Isaiah 10:21

"A remnant shall return, [even] the remnant of Jacob, unto the mighty God." — Isaiah 10:21 (ASV)

The remnant shall return ... —The very form of the words (Shear-jashub) shows that the prophet had the “Immanuel” promise in his thoughts, just as the mighty God (the same word as in Isaiah 9:6) must have reminded men of the Child who was to bear that name in the age to come. (Compare to Hezekiah’s proclamation in 2 Chronicles 30:6.)