Isaiah 37:21
21Then Isaiah the son of Amoz sent to Hezekiah, saying, “The LORD, the God of Israel says, ‘Because you have prayed to me against Sennacherib king of Assyria,
Wesley: Isaiah's prophecy. Then Isaiah the son of Amoz sent unto Hezekiah: whereas thou hast prayed to me against Sennacherib king of Assyria. 14–20. The history related here is, almost in the same words contained 2 Kings 19.
God’s answer comes “because you prayed.” Arminian readers see prayer as a cause in the story; the deliverance is given in response to Hezekiah’s petition.
Calvin: then Isaiah sent to Hezekiah. This shews the result of the prayer; as soon as matters have come to an extremity, God suddenly holds out his hand to assist the pious king by the Prophet Isaiah. Not that he immediately stretches out his arm to drive away the enemies, but he promises deliverance by the mouth of the Prophet, and thus calls even now into exercise the faith of his servant. Since thou hast prayed to me: God grants it as an answer to the prayers of Hezekiah.