John Calvin Commentary Isaiah 37:20

"Now therefore, O Jehovah our God, save us from his hand, that all the kingdoms of the earth may know that thou art Jehovah, even thou only." — Isaiah 37:20 (ASV)

And now, O Jehovah our God. At the conclusion of his prayer, the pious king now rises above the fear with which he had struggled, for the aids by which he had until now fortified himself undoubtedly encouraged him boldly to add this short clause. Although God does not always deliver His people from temporal evils, yet because He had promised that He would be the protector of the city, Hezekiah could firmly believe that all the efforts of that wicked tyrant, directed to the destruction of that city, would be fruitless.

May know that you alone are Jehovah. When he pleads it as an argument with God that the deliverance of the city will be an occasion for promoting His glory, we conclude that nothing is more desirable than to make His name glorious in every possible way. This is even the chief purpose of our salvation, from which we must not depart if we desire God to be gracious to us.

Hence we conclude that those people are unworthy of His assistance who, satisfied with their own salvation, disregard or forget the reason why God chooses to preserve them. Not only do they dishonor God by this ingratitude, but they also inflict grievous injury on themselves by separating those things which God had joined; for in saving His people, He glorifies His name, which must be, as we have already said, our highest consolation.

Besides, Hezekiah does not only desire that the God of Israel hold a certain rank, but that all idols be abolished, and that He reign alone. For at that time many idolaters would have allowed Him to be worshipped along with others; but, since He does not admit companions, every deity formed by human hands must be destroyed, so that He may hold the undivided sovereignty.