Run, John, run, the law commands
But gives us neither feet nor hands,
Far better news the gospel brings:
It bids us fly and gives us wings
The law tells us what we need to do and condemns us when we fail. It provides no help in the process. The law is like a burden upon our back.
The gospel, on the other hand, tells us to go further than the law (i.e. to love completely). But, the gospel empowers us to live this way.
(There is some uncertainty about who wrote it.)