It is correct to perform iʿtikāf in Masjid al-Ḥarām, Masjid al-Nabī (Ṣ), Masjid al-Kūfah, and Masjid al-Baṣrah. Similarly, it is correct to perform iʿtikāf in the jāmiʿ mosque of every town, except when the religious leadership (imāmah) of that mosque is in the hands of a person who is not dutiful (ʿādil), in which case, based on obligatory precaution, iʿtikāf is not correct.
A jāmiʿ mosque is one that is not particular to people of a specific locality, area, or group; rather, it is a place where people of different areas and localities of the town gather and frequent. The legality (mashrūʿiyyah) of iʿtikāf performed in any mosque other than a jāmiʿ mosque is not established; however, there is no problem in performing iʿtikāf in other mosques with the intention that it being a desirable act is probable.
As for performing iʿtikāf in a place that is not a mosque – for example, in a place that is a ḥusayniyyah[3] or only a prayer room – it is not correct and has no legal basis. vii. Iʿtikāf must take place in one mosque.