“That which you have prayed to me.” 2 Kings 19:20 differs from Isaiah 37:21 somewhat. Given the sentence itself, the relative particle asher, translated “that which” here in 2 Kings means “because” in Isaiah because the concluding phrase “I have heard” is not in Isaiah. We must not see 2 Kings 19:20 and Isaiah 37:21 as being a contradiction of what Isaiah said, any more than we should think that Hezekiah, in that desperate time, only prayed a prayer that was five verses long (2 Kings 19:15-19); Hezekiah would have prayed a much longer prayer that that. Almost always, what is recorded in the Bible is the core of what was said or done, and that gives us an understanding of the situation. There is no need for us to know every word that was spoken or action that was taken in these situations, in fact, that would be a distraction. In this case, 2 Kings and Isaiah give us an important picture of prayer: in 2 Kings, God lets us know that He hears what we pray (“I have heard”). In Isaiah, God lets us know that the fact that we do pray is important (“Because you have prayed to me”).