Letter's of Peter are two ancient letters written by Jesus right-hand man Peter Simon.
In Peter's first letter he tell his followers to live good lives and follow the law. He admits that it's a shame that their good deeds are not rewarded by God, but that the reward will come eventually, perhaps in the next life.
In Peter's second letter he suspects that he won't live much longer and he warn people against switching from Christianity to another religion as that's a one way ticket to hell.