John Gill Commentary Isaiah 37:35

"For I will defend this city to save it, for mine own sake, and for my servant David`s sake." — Isaiah 37:35 (ASV)

For I will defend this city to save it
Or, "shield it"; and if God will be the shield and protection of any place or people, they must needs be safe; who can hurt them?

For my own sake, and for my servant David's sake ;
not for the merits of the inhabitants of it, but for the sake of his own name and glory, who had been blasphemed by the Assyrian monarch, and his general; and for the sake of his servant David, in whose seed he had promised the kingdom should be established; see (2 Samuel 7:12–16) and chiefly for the sake of the Messiah, David's son, and the Lord's servant, who was to spring from Hezekiah's race, and therefore must not be cut off.