Question: Is it permissible to perform salat in a cemetery, church, public bath, or at a place that is likely to be impure?
ANSWER
It is makruh to perform salat facing najasat that is not covered and facing a grave. It is makruh to perform salat at places that are likely to be impure, such as in a cemetery, public bath, or church. It is not makruh to perform it after cleaning and washing such places. If one is unable to find anywhere to perform salat, in this case it is permissible to perform salat in a church. But one must leave it immediately after salat because the church is a place where devils meet together. If the church is purged of the symbols of disbelief, it will not be makruh to perform salat there. (Radd-ul-mukhtar)

A hadith-i sharif declares: “Curse be upon those who perform salat on a grave.” To perform salat on a grave is to imitate Jews. Therefore, it is makruh. It is written in the books Haniyya and Hawi that it is not makruh to perform it at those parts of a cemetery where there are no graves. If the grave is behind the worshiper or in front of him but so far that it would be permissible for someone else to pass in front of him within such a distance, it is not makruh, either. Also, to turn the graves of prophets or pious Muslims into mosques is to imitate Jews. Because it is like attributing a partner to Allahu ta’ala in worship, our Prophet prohibited it and prayed: “O my Rabb! Don’t make my grave an idol that is worshiped.” But if a mosque is made close to a deceased pious Muslim or if one performs salat at a place close to his grave thinking that one will attain Allah’s mercy through him or that one’s worship will be useful to him also and if one does not think of performing salat facing him out of respect, it is not harmful at all because Hadrat Ismail’s (’alaihis-salam) grave is in a place called Hatim, which is close to Ka’ba. The most valuable salat performed in Masjid al-Haram is the one performed at that place. (Hadiqa)

It is makruh to perform salat facing a grave in front of which there is no barrier like a curtain or wall. (Ma’rifatnama)

It is not makruh to perform salat if there is a curtain or wall between the qibla of the mosque and the grave or if the grave is on one side of or behind the worshiper. (Fatawa-i Hindiyya)

A hadith-i sharif says:
(Do not sit on graves and do not perform salat toward them.) [Nasai]