Christians and Muslims both believed that the plague was sent by a higher power. Ironically, they both also believed that it was God sending a message to punish the people for what they had done wrong.
During the time of the plague, many people could not understand where it came from. Initially people believed that it was caused by an alignment with planets. Some other theories were that the Jews came to poison the Christians, evil deamons were about in the towns, and the earth was letting out fumes. There must have been some other cause such as, for instance, the will of God, or corrupt humours and the badness of air and earth; although perhaps such poisonings, where they did occur, were a contributory factor. (251) Eventually, most religions settled on a common cause. God. Both Christians and Muslims alike felt that God was trying to punish them.
Most people felt that it was God, upset from all of the sins committed. Muslims stated that It is punishment that God inflicts on whom he wills, but He has granted a modicum of clemency with respect to Believers. (253) The Christians had a like statement, claiming It should be known to all Christians that pestilence, and every other manifestation of Gods vengeance arises because of sin Pestilence arises from multitude a of sins, must most especially from swearing worthless, deceitful and meaningless oaths. (258).
Although the real reason for the Plague is awfully unclear still to this day, people do know that it was spread by rats. The Christians and the Muslims believed that Gos was hurting them for betraying him.