From the point of rights and law, social classes and individuals in Islam are equal like the teeth of a tomb. The social discrimination of the pre-Islamic age of ignorance (like racial discrimination) has been abolished. Social discrimination in Islam (i.e. privilege in nobility, and not in law) does exist, but it is in accordance with piety and knowledge.
Allah the Most High said: “O you men, surely We have created you of a male and a female, and made you tribes and families that you may know each other; surely the most honourable of you with Allah is the one among you most careful (of his duty); surely Allah is Knowing, Aware.”
He also said: “O you who believe, be maintainers of justice, bearers of witness for Allah’s sake, though it may be against your own selves or (your) parents or near relatives; if he be rich or poor, Allah is nearer to them both in compassion; therefore do not follow (your) low desires, lest you deviate; and if you swerve or turn aside, then surely Allah is aware of what you do.”
He also said: “Say: Are those who know and those who do not know alike? Only the men of understanding are mindful.”
He also said: “Is he then who is a believer like him who is a transgressor? They are not equal,”
On the day of the conquest of Mecca, the Holy Prophet Muhammad (S) stood up among the people to preach to them; first he praised Allah, magnifying Him, then he said: “O people let those who are present convey my message to those who are absent. Surely Allah the Holy, the Exalted has removed the arrogance and mutual boasting about fathers and tribes of the pre-Islamic age of ignorance. O people, you are from Adam and Adam is from clay. Beware that the best of you with Allah and the most honourable with Him are those who are most pious and who obey Him the most.”
He (S) also said: “Surely Allah through Islam removed the arrogance and the mutual bragging about their fathers of the pre-Islamic age of ignorance. Beware that all people are from Adam, and Adam himself is from clay. And the most noble of you with Allah are those who have more piety.”
He (S) also said: “Surely people from the period of Adam until now are like the teeth of a comb: there is no superiority of an Arab over a non-Arab and of the red over the black except on the basis of piety.”