I am going to take this bucket of water and pour it on the flames of hell, and then I am going to use this torch to burn down the gates of paradise so that people will not love God for want of heaven or fear of hell, but because He is God.

This quote is talking about removing the incentives of religion and taking away the fear of going to hell or the promise of going to heaven. The bucket and torch in the quote are metaphorical. The idea is that by destroying the gates of heaven, so no one can gain access, people will only love and follow God because He is God and not because it will gain them rewards or avoid punishments.