Is a Kohen who sins allowed to serve in the Temple?
If a Kohen becomes an apostate, his service is invalid; see
Ezekiel 44:12-13. A Kohen who is a chronic sinner should not
be allowed to serve (Aruch Ha-Shulchan He-Asid, Bi'as Mikdash
49:8) unless he repents. The Talmud (Berachos 32a) tells us
that a Kohen who has committed murder should not bless the
people. This would imply that he should not perform any Temple
service; but Tosafos (Yevamos 7a) rules that if he does so, the
service is valid.
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