Prayer: Making the Shrines of the Imams Impure and the Duty to Purify Them
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 890
It is unlawful to make the shrines of the Infallible Imams (ʿA) impure. If one of the shrines becomes impure, in the event that it remains impure is disrespectful, it is obligatory to make it pure. In fact, the recommended precaution is that even if it is not disrespectful, it should be made pure.