Muhammad (peace be upun him) laid the foundations for tolerance among people. In the Qur'an, Allah revealed to His Prophet(peace be upun him) that there must be no compulsion in the acceptance of religion. Muhammad (peace be upun him) also clarified rights of the non-Muslims who do not wage war against Muslims, and guaranteed protection of their lives, children, property and honor. Even today, there are Jewish and Christian citizens living in peace and security in many Muslim countries; quite different from the Spanish Inquisitions in which Muslims and others were exterminated in an ethnic cleansing that violated all the humanitarian principles asserted by western culture.
Among the greatest principles of religion brought by Muhammad (peace be upun him), the Prophet of Mercy, was that acceptance of Islam, whether by individuals or groups, is left to personal conviction, and that invitation to it is based upon wisdom and good advice, not on compulsion by the sword or any other means. This is mentioned in many places in the Qur'an and in the prophetic teachings (Sunnah). For example, Allah said in the Qur'an:
"There shall be no compulsion in [acceptance of] the religion. The right course has become clear from the wrong. So whoever disbelieves in false objects of worship and believes in Allah has grasped the most trustworthy handhold with no break in it. And Allah is Hearing and Knowing." (2:256)
And He said:
"And say, 'The truth is from your Lord, so whoever wills – let him believe; and whoever wills – let him disbelieve.'" (18:29)
Additionally, the religion conveyed by Muhammad (peace be upun him) was concerned about non-Muslims. It prohibited killing them outside of battle and actually allowed for righteousness and kindness toward them. For the Qur'an states:
"Allah does not forbid you from those who do not fight you because of religion and do not expel you from your homes – from being righteous toward them and acting justly toward them. Indeed, Allah loves those who act justly." (60:8)
And among the greatest principles established by Islam is respect for the rights of non-Muslims, whether they are under the protection of an Islamic state or outside of it, as long as they do not declare war against Islam or Muslims. Each of them has rights that must be upheld by all Muslims just as they protect themselves, their properties, their women and their children. No Muslim is permitted to transgress against them in any way. The Messenger of Allah (peace be upun him) said,
"He who kills one protected under a treaty will not smell the fragrance of Paradise. And indeed, its fragrance is found from the distance of forty years [of travel]."
And he (peace be upun him) said,
"Surely, a person who wrongs one protected under a treaty or belittles him, overworks him or takes something from him against his will, I will be his opponent on the Day of Resurrection."
In fact, Muslims and non-Muslims are equal before the judge in a court of law. Al-Ash`ath reported:
"There was a dispute between me and a Jewish man over a piece of land, so I took him to the Prophet (peace be upun him), blessings and peace be upon him, who said, 'Do you have any evidence?' I said, 'No.' He said to the Jew, 'Swear an oath.' I said, 'O Messenger of Allah (peace be upun him), when he swears to it he will take my property.'
Thereupon, Allah revealed the verse:
"Indeed, those who exchange the covenant of Allah and their oaths for a small price will have no share in the Hereafter, and Allah will not speak to them or look at them on the Day of Resurrection, nor will He purify them; and they will have a painful punishment." (3:77)
This condition has continued in Muslim lands up to the present day. Jews, Christians and followers of other religions have lived in Muslim regions enjoying security, justice and tolerance seldom found elsewhere. The mass extermination of members of a particular race or religion, as still witnessed in some countries, is further evidence of the value of what Islam offered to others. Conversely, Muslims have suffered greatly as objects of ethnic cleansing and religious persecution; the most infamous of them being the Spanish Inquisitions. They did not even spare Christians of other denominations, not to mention Jews and others, who subsequently found a secure refuge in various Muslim lands.