Interesting confession question

[PrayPsalm51]

Father, a priest once told me they( the priests) have to do the penances they assign as well. that does not make sense to me… Can you elaborate?

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I read that too somewhere and I asked my priest about it. He described it as a pious thing for the priest to do to offer penances for all the confessions he has heard. He also said that he once mentioned it in his OWN confession and was told it wasn’t a sin (to not do penances on behalf of the penitants). Still he feels he needs to offer something on behalf of the penitants. I’m grateful and feel a little guilty for his burden all at once.