Isaiah 39 is how Isaiah wants us to remember Hezekiah. We are not to remember him as a good king but as mortal (Isaiah 38) and especially as fallible (Isaiah 39). Not even just able to make mistakes, but that he made mistakes and one huge one at that. The big blunder that Isaiah made was falling for the political niceties of Babylon and showing them everything that he had. Babylon was looking for allies against the Assyrians, but it was a foolish move for Hezekiah to trust them. Isaiah showed him this by asking him questions and because Hezekiah repented the punishment was delayed for a future generation. Hezekiah would go on to do good and great things, like standing up to Assyria (Isaiah 36) and offering that wonderful prayer (Isaiah 37). These things chronologically took place after Isaiah 39, but Isaiah does not want us to remember him that way. The reason? Isaiah wants to point us to the Messiah who will live on the throne forever and never make a mistake: Jesus. What kind of legacy will you leave? Will you only leave death and fallibility for your children or will you pass along the treasure of the kingdom of God in heaven?