Praise be to Allah, prayer and peace be upon the Messenger of Allah and upon all his family and companions.
Every part of the earth, which is valid for performing prayer (Salah) , is a Mosque (Masjid) for the Prophet ( PBUH) said: “The earth has been made for me (and for my followers) a place for praying and a thing to perform Tayammum.” { Al-Bukhari }.
The Masjid which is governed by jurisprudential (Fiqh) rulings, is the place endowed (Muquf for prayer i.e. specifically restricted for praye. As for the Musalla (area allocated for prayer), it is the place of Salah and supplication, and it does not have to be endowed ( Muquf), but could be so among other things .Therefore, the Musalla includes the Masjid and other places since every Masjid is a Musalla, but not every Musalla is a Masjid. The Masjid differs from the Musalla in the following aspects:
First: The Masjid – as we have mentioned - : is the place allocated for prayer, thus cannot be sold and the like. Al-Imam Al-Nawawi said: “The possession of the (Muquf) becomes that of Allah. “ { Minhaj Al-Talibeen pp.170 }.However, a Musalla can be sold, or transferred to somewhere else and can be a rented place.
Second: A menstruating woman and a ritually impure person ( Junub) are prohibited from staying in the Masjid ;whereas, they are allowed to stay in the Musalla. Al-Imam Al-Nawawi said: “ What is prohibited in the state of minor impurity ( requires ablution ) is definitely prohibited in the state of major impurity (requires Ghusul-purificatory bath) i.e. these people are allowed to pass through the Masjid, but they are not allowed to stay in it” {Minhaj Al-Talibeen vol.1, pp.12)}.