The church needed money so they came up with a method called indulgences. It was the selling of relaxation of penalties for sins people have committed. People didn't like this method. It was basically a ticket to heaven

Indulgences reduced punishment in purgatory. Purgatory was a place where souls went before they were sent to heaven. In purgatory the souls were punished for the sins they had committed. It enraged the Christians that punishment could be reduced.

Indulgences and Purgatory