For the devotee, if he has rendered a little service to Krsna even for a moment, the life of human life next is guaranteed. Guaranteed in this way, that if he unknowingly commits some mistake, then it is guaranteed. And if he knowingly commits mistake, then he is going to be cats and dogs. If one purposefully commits mistake and sinful life, "Now I am chanting Hare Krsna. I can do all sinful life; it will become counteracted," that rascal will be punished very, very much.

Srila Prabhupada — December 5, 1975.