Reference: Sharh ‘Umdatil-Fiqh – Tape No.8, Question No.24
Question: If the caller to prayer (mu.adhdhin) is in a state of major ritual impurity (janaabah), is it permissible for him to enter the masjid so he can call the adhaan?
Response: Yes, he may enter the masjid; that is because he will not be sitting down. That which is prohibited [whilst in the state of janaabah] is for him to sit down [inside the masjid]. As for entering the masjid for a necessity, and then leaving, then there is no harm [in doing so], [because] there is no sitting down [when calling] the adhaan.