Tzaraat prevents a Metzora from performing Temple Service: Shabbat 132a-b
The Metzora stands at the Nikanor Gate during the purification process: Sotah 7a, 8a; Zevachim 32b
Permitting a metzora to stand at the Nikanor Gate for his purification even if he is also impure for some other reason: Zevachim 32b
The concern for using one item for two mitzvot simultaneously, if one Kohen purifies two people with tzaraat simultaneously: Sotah 8a
