Poor pope Paul read this like..."if by the belt you mortify the deeds of the flesh, you shall live." So, in Catholic theology the belt = Spirit? That's more perverse than I thought.
It is good that you read. Now lets us work on understanding. The belt is, of course, the tool of mortification, not the motivator. The Spirit is, in the days of St. Paul, and of the days of John Paul, what moves us to read the Bible and do what it says. Try it one day.