John Gill 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)

Now therefore, O Lord our God, save us from his hand The hand of the king of Assyria. The Lord has promised that he would and Hezekiah believed he would; but he knew that for this he would be inquired of by him, and he pleads covenant interest, in him, and entreats for salvation upon that account, as well as for the reason following:

that all the kingdoms of the earth may know that you are the Lord, even you only ;

by doing that which other gods could not do; they could not save the nations that worshipped them from the hand of the Assyrians; if therefore the God of Israel saved his people from them, this would be a proof to all the world that he is God and there is none besides him.