✅Answer: Please pay attention to the following narrations:

1 عَنِ الْعِيصِ بْنِ الْقَاسِمِ قَالَ: سَأَلْتُ أَبَا عَبْدِ اللَّهِ عَنِ الْبِيَعِ وَ الْكَنَائِسِ يُصَلَّى فِيهَا فَقَالَ نَعَمْ وَ سَأَلْتُهُ هَلْ يَصْلُحُ بَعْضُهَا [نَقْضُها] مَسْجِداً فَقَالَ نَعَمْ.

📚 Al-Tahdhib, vol. 2, p. 222

'Is bin Qasim said: I asked Imam al-Sadiq (peace be upon him) about Christian churches and Jewish temples (places of worship), and if one can pray in them? He said: 'Yes!'

And I asked if it is permissible to convert some of them into a mosque? He said: 'Yes!'

2 عَنِ الْعِيصِ قَالَ: سَأَلْتُ أَبَا عَبْدِ اللَّهِ عَنِ الْبِيَعِ وَ الْكَنَائِسِ هَلْ يَصْلُحُ نِقْضُهُمَا لِبِنَاءِ الْمَسَاجِدِ فَقَالَ نَعَمْ.

📚 Al-Kafi, vol. 3, p. 368

'Is said: I asked Imam al-Sadiq (peace be upon him) about Christian churches and Jewish synagogues (temples), and if it is permissible to demolish and dismantle them to build mosques? He said: 'Yes!'

3 عَنِ الْحَلَبِيِّ عَنْ أَبِي عَبْدِ اللَّهِ فِي حَدِيثٍ قَالَ: سَأَلْتُهُ عَنِ الصَّلَاةِ فِي الْبِيعَةِ فَقَالَ إِذَا اسْتَقْبَلْتَ الْقِبْلَةَ فَلَا بَأْسَ بِهِ.

📚 Al-Kafi, vol. 3, p. 388

Halabi said in a narration: I asked Imam al-Sadiq (peace be upon him) about praying in a Jewish temple. The Imam said: 'There is no problem as long as you face the qiblah (direction of prayer)!'

4 عَنْ عَبْدِ اللَّهِ بْنِ سِنَانٍ عَنْ أَبِي عَبْدِ اللَّهِ قَالَ: سَأَلْتُهُ عَنِ الصَّلَاةِ فِي الْبِيَعِ وَ الْكَنَائِسِ وَ بُيُوتِ الْمَجُوسِ فَقَالَ رُشَّ وَ صَلِّ.

Al-Tahdhib, vol. 2, p. 222

Abdullah ibn Sinan said: I asked Imam al-Sadiq (peace be upon him) about praying in Jewish temples, Christian churches, and the houses of the Majus (Zoroastrians). The Imam said: 'Sprinkle the place with water and pray!'

✅ From the above narrations and others, it is clear that there is no problem with building a mosque in the place of a Jewish temple or a Christian church. Also, it is permissible to pray in a Christian church, a Jewish temple, and the houses of the Majus as long as one faces the qiblah. It is also recommended to sprinkle the place with water and then pray in it.

اللَّهُمَّ فَصَلِّ عَلَی مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ عَجِّلْ لِوَلِیِّکَ الْفَرَجَ وَ الْعَافِیَةَ وَ النَّصْرَ