My memory of this is fairly thin. But I know it's real and I read it in probably an anthology. I think it might have been fairly short. The concept of the sin eater pops up in other literature from time to time as well. Unfortunately I am unable to cite examples. I think I remember references to sin eaters being members of a caste. The idea as best I can explain is that the sin eater agrees to take on the responsibilities, guilt and karmic costs of a sin committed by another person either as a duty related to the sin eaters cast, or in exchange for money or valuables. The person or entity that originally committed the sin is then free of the consequences. I think this story was written before 1965.