It may be the Lord thy God - The God whom thou dost serve, and in whose name and by whose authority thou dost exercise the prophetic office.

Will hear the words - Will come forth and vindicate himself in regard to the language of reproach and blasphemy which has been used. See a similar use of the word 'hear' in Exodus 2:24; Exodus 3:7.

To reproach the living God - The revilings of Rabsbakeh were really directed against the true God. The reproach of the 'living God' consisted in comparing him to idols, and saying that be was no more able to deleted Jerusalem than the idol-gods had been able to defend their lands (see the note at Isaiah 36:18). The phrase 'the living God' is often applied to Yahweh in contradistinction from idols, which were mere blocks of wood or stone.

For the remnant that is left - For those who survive; or probably for those parts of the land, including Jerusalem, that have not fallen into the hands of the Assyrian. Sennacherib had taken many towns, but there were many also that had not yet been subdued by him.

Isaiah 37:4 Parallel Commentaries

Christ Rightly and Properly Said to have Merited Grace and Salvation for Us.
1. Christ not only the minister, but also the author and prince of salvation. Divine grace not obscured by this mode of expression. The merit of Christ not opposed to the mercy of God, but depends upon it. 2. The compatibility of the two proved by various passages of Scripture. 3. Christ by his obedience truly merited divine grace for us. 4. This grace obtained by the shedding of Christ's blood, and his obedience even unto death. 5. In this way he paid our ransom. 6. The presumptuous manner in which …
John Calvin—The Institutes of the Christian Religion