Muslims entering non-Muslim places of worship

Question: Is it permissible for a Muslim to enter a church to know of their prayers or listen to a lecture?

Answer: A Muslim is not allowed to enter the places of worship of disbelievers as this leads to increasing their number. It was reported by Al-Bayhaqee with a sound chain of transmitters on the authority of `Umar (may Allaah be pleased with him) who said… read more here.

Non-Muslims entering Mosques

Question: What is the ruling on non-Muslims entering a Masjid (mosque) or Musallah (a place for Prayer), whether to attend the Salaah (Prayer) or to listen to a lecture?

Answer: When we answered Fatwaa no. 2922, we stated that it is Haram (prohibited) for Muslims to let any Kaafir (disbeliever) enter Al-Masjid Al-Haram (the Sacred Mosque in Makkah) or any part of the Sanctuary, because Allaah (Exalted be He) says… read more here.