Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa., – Volume 6, Page 267, Fatwa No.2393
Question: Is it permissible to buy a church and convert it to a masjid, after removing the crucifixes and pictures, both hung and engraven?
Response: Yes, it is permissible to buy it and make it into a masjid, and it is obligatory to remove the crucifixes and pictures, both hung and engraven, as well as everything that would indicate that it is a church, and we do not know of anything preventing that from being done.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet Muhammad ﷺ and his family and his companions.