There is a story of a king who sent his son a great distance to study all the wisdom of the world. The son went, studied, and returned wise. One day the king asked his son to take a massive rock and place it up upon the roof of the house. But the rock was too huge, and the king’s son was unable to lift the rock. Unable to fulfill his father’s request, the king’s son was … terribly upset.
When his father found him sulking in his room the king said to him, “You thought I wanted you to lift that giant stone? Even with all your wisdom you thought I asked you to do something as impossible as that!? All I intended was for you to take a hammer and break the stone up into a bunch of little pieces – then you could have placed the stone on the roof!”
Just like this, God commands us to lift our hearts up to heaven. But our hearts are these giant heavy stones – totally impossible to lift. All you can do is take a hammer – which is speech – and shatter the stony heart. Thus you can lift your heart up to heaven.