Another matter that has confused some people is this: a person may deal with a bank or engage in other activities whose earnings are unlawful, then build a mosque or repair a road. Someone may then ask: “May I pray in this mosque which was repaired by a man whose wealth is unlawful, or walk on this road?” We hold that there is nothing wrong with praying in this mosque, even if it was financed by usurious funds or other unlawful earnings, for its sin rests upon the one who acquired it. Moreover, we may say: perhaps the man who built the mosque has repented and built it in order to rid himself of the sin and unlawful earnings. Thus, if we pray there and encourage him, we will be helping him to repent.

A person must judge matters by the معیار of the Sacred Law and sound reason, not by blind emotion. Nothing harmed the Muslims—even in the time of the Companions, may Allah be pleased with them—more than blind emotion. What drove the Khawarij to rebel except blind emotion and their claim that Ali ibn Abi Talib, may Allah be pleased with him, had betrayed [the Muslims], that he had to be fought, and that he had committed disbelief by accepting arbitration, and similar claims?

If, however, someone usurped land and built a mosque upon it, then we should not pray in it. According to those who hold that prayer on usurped land is invalid, we do not pray there because we do not seek nearness to Allah, Most High, through something invalid. But according to those who regard prayer on usurped land as valid, we likewise say that one should not pray there. We do not say that the prayer is invalid; rather, we say that this would encourage that unjust usurper to seize the Muslims’ property and then boast that he has built a mosque upon it.