Question: Is it permissible to perform Salaah (Prayer) in a Masjid (mosque) that contains a grave? Is it obligatory to kiss the entry threshold of Masjid Al-Husayn and Masjid Al-Sayyidah Zaynab, kiss their shrines, beseech Allaah by them, and seek strength and support from them? Is it permissible to travel from one place to another to commemorate the birthdays of pious people?
Answer: Firstly, if a Masjid is built over a grave, it is not permissible to offer Salaah there. The same applies if someone was buried in a Masjid after it was built. It is obligatory that the buried remains be moved to a public cemetery, if this is possible. This is based on the Hadeeths that indicate the prohibition of praying in Masjids that contain graves… read more here.