Islam's rapid spread continued even after the Prophet's (may Allah bless him and grant him peace) death. Within a few decades, Islam spread to all of Mesopotamia and North Africa, and reached Spain in the west and India in the east.
Within 100 years, the Muslim empire spread over an immense area and firmly established itself. In this huge geographic area, many different religious denominations existed side by side. Most of them, however, were composed of Christians and Jews. The Muslims, as a general rule, were always very tolerant toward all religious groups in their lands, did not force people to embrace Islam, and respected every person's freedom of conscience, for the Qur'an says:
There is no compulsion where religion is concerned. (Surat al-Baqara, 256)
Churches and synagogues were protected. At a time when enforced proselytization was a common practice, such tolerance was unique.
One of the most extraordinary examples of this tolerance was the conquest of Jerusalem. The patriarch of the city's Church of the Holy Sepulcher feared that his church would be destroyed by the Muslims. Thus, Caliph `Umar visited the church and said that there was nothing to worry about. When the time for prayer came, he asked the patriarch for permission to leave so that he could pray nearby. The al-Aqsa mosque was built later on that very spot.
The Muslims gave Jerusalem one of the world's most spectacular works of architecture: the Qubbat as-Sakhrah (Dome of the Rock), which was built on the rock believed to be the place from where Prophet Mohammed (may Allah bless him and grant him peace) ascended to the heavens. The stunning motifs and golden dome of this architectural masterpiece reflects Islam's sense of art and civilization.
During the Umayyad era, many Christians in Damascus (Sham) occupied important positions in the state bureaucracy and fulfilled their religious obligations as they wished. Some wrote even books that criticized Islam and Muslims without fear of retribution.
At the same time, Europe was governed by a dark fundamentalism and barbarism. The Catholic Church was oppressing the Jews and even Christians of other denominations. Forced proselytization, as well as torture and murder in the name of religion, were common. On the other hand, Muslims have always treated the People of the Book (Jews and Christians) with tolerance and compassion, for Allah orders this in the Qur'an.
Throughout the history of Islam, its tolerance toward Jews and Christians continued. Jews fleeing the terror of the Spanish Inquisition found refuge and tolerance on Ottoman soil. The source and reason for such tolerance was the morality of the Qur'an, for Muslims are told:
Only argue with the People of the Book in the kindest way—except in the case of those of them who do wrong—saying: "We believe in what has been sent down to us and what was sent down to you. Our Allah and your Allah are one, and we submit to Him." (Surat al-‘Ankabut, 46)