What is the ruling concerning a Muslim who resides in a Christian area and works in construction there, and has not prayed in a mosque throughout his stay? Is he obligated to change his place of residence despite the remoteness of Muslim areas?

If there is no mosque in the area, or if it is too far away so that the adhan (call to prayer) cannot be heard without a loudspeaker, then there is no sin upon the Muslim for not praying in the mosque, even according to those who hold that congregational prayer is obligatory. And if the town is inhabited only by Christians, it is better to leave it and move to a town inhabited by Muslims, due to the potential corruption of a Muslim's faith that may result from residing among polytheists. However, it is not obligatory to leave unless one fears for oneself tribulation (fitna) or is unable to establish the rituals of the religion. Therefore, it is advisable to move to a town inhabited by Muslims or where Muslims are numerous.