When we answered Fatwa no.2922,we stated that it is Haram (prohibited) for Muslims to let any Kafir (disbeliever) enter
Al-Masjid Al-Haram (the Sacred Mosque in Makkah) or any part of the Sanctuary, because Allah (Exalted be He) says:
O you who believe (in Allâh’s Oneness and in His Messenger Muhammad صلى الله عليه وسلم)! Verily, the Mushrikûn (polytheists, pagans, idolaters, disbelievers in the Oneness of Allâh, and in the Message of Muhammad صلى الله عليه وسلم) are Najasun (impure). So let them not come near Al-Masjidal-Harâm (at Makkah) after this year
Some Fuqaha' (Muslim jurists) say that it is permissible to let non-Muslims enter other Masjids, because there is no evidence prohibiting this. (Part No. 2; Page No. 117) Other Fuqaha' deem it as impermissible, on the basis of Qiyas (analogy) with
Al-Masjid Al-Haram. The correct opinion is that it is permissible for a religious benefit and if necessity calls for it; for example, to hear something that may encourage them to embrace Islam or to meet their need to drink water in the Masjid.