Da`wah to Allah is the way of the Messengers of Allah

Q: It is obligatory for every Muslim to perform Da`wah (calling to Islam) and invite their neglectful brothers, who are preoccupied with amusements and worldly pleasures, back to the Din (religion). Here in Algeria we organize campaigns to go and invite the people to the Masjid (mosque) to remind them, as Allah says: Therefore remind (men) in case the reminder profits (them). (Surah Al-A`la, 87:9), to help to stop their negligence, by the Permission of Allah. However, some shaykhs in Algeria say that it is Haram (prohibited) to let people who are not in a state of Taharah (ritual purification) enter the Masjid. We would like to ask Your Eminence whether this claim is true or not. Please advise as soon as possible.

A: Da`wah to Allah is the way of the Messengers of Allah, the last of whom was Muhammad (peace be upon him), as Allah (Glorified and Exalted be He) says: Say (O Muhammad صلى الله عليه و سلم): "This is my way; I invite unto Allâh (i.e. to the Oneness of Allâh - Islâmic Monotheism) with sure knowledge, I and whosoever follows me (also must invite others to Allâh i.e. to the Oneness of Allâh - Islâmic Monotheism with sure knowledge). And Glorified and Exalted be Allâh (above all that they associate as partners with Him). And I am not of the Mushrikûn (polytheists, pagans, idolaters and disbelievers in the Oneness of Allâh; those who worship others along with Allâh or set up rivals or partners to Allâh)." (Surah Yusuf, 12:108). Da`wah can be directed towards an individual or groups in a Masjids, clubs, universities, schools, or other places where people gather. Da`wah is a general term and it can be directed to Kafirs (disbelievers), Fasiqs (those openly and flagrantly violating Islamic law), and Mu'mins (believers). (Part No. 3; Page No. 379) A Kafir may repent of their Kufr (disbelief), a Fasiq may relinquish their disobedience; and a Mu'min may increase their Iman (Faith) and insight. It is not a problem if a non-Muslim enters a Masjid, if this achieves a Shar'y (Islamic legal) benefit, such as the hope that they might accept Islam if they hear a religious lecture or attend a Halaqah (learning circle). It is authentically reported from the Prophet (peace be upon him) that he ordered Thumamah ibn Uthal Al-Hanafy to be tied in one of the columns of Al-Masjid Al-Nabawy (the Prophet's Masjid), even though he was a Kafir, and he was guided by Allah to accept Islam. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.