Halakhah zu Wajikra 22:2

That an impure priest not serve: That a priest not serve when he is still impure, as it is stated (Leviticus 22:2), "and they shall separate from the holy things of the Children of Israel and they shall not profane My holy name." And they, may their memory be blessed, said in the ninth chapter of Sanhedrin 83b, "From where [do we know] about an impure one who served that he is [punished] with death" - meaning to say, with death by the hands of the Heavens? "As it is written, 'Speak to Aharon and to his sons, and they shall separate from the holy things of the Children of Israel and they shall not profane'"; and it is written in another place (Leviticus 22:9), "and die for it, since they profaned it."