The Prophet Muhammad, may the mercy and blessings of God be upon him, during his Last Sermon in Mina, said: “O people! Your Lord is one Lord, and you all share the same father. There is no preference for Arabs over non-Arabs, nor for non-Arabs over Arabs. Neither is their preference for white people over black people, nor for black people over white people. Preference is only through righteousness.” Then he said: “Have I conveyed the message?” and the people declared that he had. 
When we study the history of the Muslim peoples, we find that one of the hallmarks of Islamic civilization – where it has historically surpassed all others – is its universality. Islamic civilization realized the greatest level of interracial and interethnic integration that existed in the world. It offered every nationality and ethnic group the chance to participate fully in the development and cultivation of the civilization that they shared.
We can verify this by looking at the great people in Muslim history who represent excellence and achievement in all of the arts, sciences, and vocations that give a civilization its character. We find that Islam’s great thinkers, leaders, artists, and achievers represent every ethnicity and nationality that came into the fold of Islam. We find Turks, Kurds, Arabs, Persians, Berbers, Africans, Indians, and Central Asians all robustly represented.
The reason for this is simple: The religion which united these people into a civilization, though its Prophet was an Arab, is not a religion for the Arabs. Prophet Muhammad (pbuh) came with a religion for all humanity. The Quran’s message is universal.
God says about His Prophet:
“We sent you not except to be a mercy for all peoples.”
God commands His Messenger:
“Say: O people! Surely I am God’s Messenger to you all, of Him whose is the kingdom of the heavens and the Earth. There is no God but He.”
God describes the Quran as follows:
“It is no less than a message unto all creation.”
Another reason why Islamic civilization achieved the ideal of universality is because Islam sets forth the principle that righteousness is the basis for the superiority of one person over another. Considerations such as color, race, lineage, and ethnicity simply do not factor in.
God declares this unequivocally in the Quran where He says:
“O humanity! We created you from a single pair of a male and a female, and made you into nations and tribes that you may know one other. Verily the most honored of you in the sight of God are the most righteous from among you.”
And it was this very principle that Prophet Muhammad (SallAllahu Alaihi Wa Sallam) made sure to declare to the people in his Last Sermon to the assembled pilgrims in Mina:
“O people! Your Lord is one Lord, and you all share the same father. There is no preference for Arabs over non-Arabs, nor for non-Arabs over Arabs. Neither is their preference for white people over black people, nor for black people over white people. Preference is only through righteousness.”
Upon saying this, he demanded of them: “Have I conveyed the message?”
Then he heard the people’s voices rise up saying: “You have conveyed it.”
This is why Islam was able to integrate a huge diversity of nations and peoples into one great and vital civilization at a time when the rest of the world had failed to do so.
It is not that others had not tried. Possibly the greatest attempt in the history before Islam was made by Alexander III of Macedon, also known as Alexander the Great. Under the tutelage of Aristotle, Alexander strove to mold a universal civilization that would bring together all of the people in his Empire under a shared Hellenistic culture and vision. To do this, he established cities in every province with the name of Alexandria, which would be centers of culture and learning that would be the wellsprings of a single Hellenistic civilization.
He also sought to unite the Greeks and the Persians into a single people through a program of intermarriage. He held a mass marriage of his senior officers to Persian and other noblewomen at Susa, which is located in what is now western Iran. He, himself, married the daughter of the Persian monarch. He actively promoted intermarriage between the peoples of his empire as a policy.
Alas, the dream of Alexander and his mentor Aristotle did not succeed. It evaporated as soon as Alexander died. The states that succeeded his empire were those of a Greek governing class over indigenous people who did not share in the culture, values, and prosperity of the rulers.
The significance of the Islamic achievement can also be compared in light of Western civilization, which was for a very long time dominated by the bane of white supremacy. Western civilization did not regard non-whites as equals and did not afford them to fully participate in that civilization as equals. Even in America, a nation of immigrants where many ethnic and racial groups are strongly represented, and where the ideal of universality would be at its greatest possibility of realization, the days of segregation are not that long past.
It is Islam that bequeathed the ideal of equality and universality to the civilization that it founded. This is truly one of the greatest achievements of Islam.
 Musnad Ahmad