A remnant shall return. This is a confirmation of the former statement. Yet in the words s'r ysvv, (Shear Yashub,) a remnant shall return, there appears to be an allusion to that passage in which Isaiah's son was called Shear-jashub. (Isaiah 7:3.) In our observations on it, we stated that this peculiar name was given him in reference to the event, that it might be regarded as a pledge of the future deliverance concerning which his father prophesied. It was necessary that the Jews should be confirmed in various ways, that they might be convinced that the Lord would at length bring them back. This is also the design of what he immediately adds -- To the mighty God; that is, to him whom the people, after having returned from their former apostasy, will acknowledge to be the guardian of their salvation. This attribute, mighty, is ascribed to God for the sake of the occasion on which the words were used. He might have thought it sufficient to have expressed power by the name 'l, (El,) God, which also signifies mighty; but he chose likewise to add to it gvvr, (gibbor,) that is, strong or mighty, in order to excite the people to greater confidence. How was it possible for the people to betake themselves to the Assyrians and Egyptians, but because they did not think that God was sufficient for them? This is the source of all evils, when we are not fully convinced that in God is everything that can be desired for our salvation.

The remnant - That is, those who shall be left after the invasion of Sennacherib.
Shall return - Shall abandon their idolatrous rites and places of worship, and shall worship the true God.
The mighty God - The God that had evinced his power in overcoming and destroying the armies of Sennacherib.

The remnant shalt return - unto the mighty God - אל גבור El gibbor, the mighty or conquering God; the Messiah, the same person mentioned in Isaiah 10:6 of the preceding chapter.

The remnant shall return,.... This is said in allusion to Shearjashub, the name of Isaiah's son, Isaiah 7:3 which signifies "the remnant shall return", and was imposed on him, to give assurance of it; meaning, either that they should return from the Babylonish captivity, as they did, or to God by repentance; or rather the sense is, they shall turn to the Lord, be converted to Christ, to the faith and obedience of him, as some of them were when he came, a few, not all, only a remnant, as it is explained in the next clause:
even the remnant of Jacob, to the mighty God; the Messiah, so called, Isaiah 9:6. The Targum is,
"the remnant which have not sinned, and are turned from sin; the remnant of the house of Jacob shall return to worship before the mighty God.''

mighty God-- (Isaiah 9:6) the God who shall have evinced such might in destroying Israel's enemies. As the Assyrians in Sennacherib's reign did not carry off Judah captive, the returning "remnant" cannot mainly refer to this time.

"The remnant will turn, the remnant of Jacob, to God the mighty." El gibbor is God as historically manifested in the heir of David (Isaiah 9:6). Whilst Hosea (Hosea 3:5) places side by side Jehovah and the second David, Isaiah sees them as one. In New Testament phraseology, it would be "to God in Christ."