Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa., – Volume 12, Page 257, Question No.2 of Fatwa No.12971
Question: There are many churches here, so is it permissible to go inside to hold discussions with the priests there? [And] is it permissible to go inside to look around and see what people do [there]?
Response: It is permissible for the people of knowledge to enter churches in order to invite the people there to Islaam. As for entering [the churches] just to look around, then this is not befitting, because there is no benefit in this. There is [also] the fear that the Muslim may be influenced by them, especially if he is ignorant about his own religion and cannot refute the confusion that they will direct towards him.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.