Guarding a Deceased by a Kohen

A Kohen whose one of the seven close relatives has passed away, can he guard the deceased?

According to those who follow the opinion of the Shulchan Aruch, he should guard him, and according to those who follow the Rema, it is forbidden. If there is a concern about mice, it is permitted, but this is uncommon among us.

A Kohen whose one of the seven close relatives has died is commanded to become impure for them, as explained in Zevachim 100. In Shulchan Aruch, Yoreh De'ah, laws of mourning, Siman 373, paragraph 5, it is written: "All those for whom he must become impure, even if not necessary. Some say only if necessary. The Rema writes that according to the first opinion, even if a relative dies on Shabbat, when it is impossible to bury him on the same day, it is permitted to become impure for him and guard him, so that he does not lie in disgrace (Terumat HaDeshen, Siman 283); and it is proper to be stringent according to the latter opinion, to become impure only for the needs of burial and bringing him a coffin and shrouds." This means that Rambam and Tosafot disagree on whether it is a commandment to become impure only when necessary or even when not necessary. The Shulchan Aruch follows Rambam's opinion that it is a commandment to become impure even when not necessary. The Rema writes that it is proper to be stringent according to Tosafot's opinion, to become impure only when necessary.