Prayer: Taking Impurities into a Mosque
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 892
Taking something that is an intrinsic impurity, or something that has become impure by secondary means (mutanajjis), into a mosque is unlawful if it causes disrespect to the mosque. In fact, the recommended precaution is that even if it is not disrespectful, an intrinsic impurity should not be taken into a mosque unless it is something that naturally comes in with a person when he enters a mosque, such as the blood of a wound that is on his body or clothing.