Question 61: There is a Christian person who stands among Muslims in rows of Salaah (Prayer). He used to imitate worshippers in their moves and learnt some Aayaahs (verses of the Qur’aan). Many trials have been carried out to make him pronounce Shahaadah (Testimony of Faith), but he completely refused. What is the ruling on letting him participate in congregational Salaah?
Answer: It is permissible to permit Christians to stand in rows of Salaah among Muslims. We are not required to expel them from it because staying among Muslims and watching the acts of worship is from the public interest… read more here.