For more on this topic, see Justice in Islam
Among all “branches” of the law, zakāt is unique in that it has a dualistic character: on the one hand, it is an integral part of religious “ritual,” and, on the other hand, it functions as a substantive legal sphere, constituting itself as a “tax law.” Inasmuch as socially based financial responsibility merges into rituality, rituality merges into the moral accountability for society’s welfare. Like the ubiquitous charitable trust (waqf), zakāt was one of the most important instruments of social justice.
O son of Adam, I sought food from you but you failed to feed Me. The man would ask: My Lord, how could I feed You when You are the Lord of the worlds? God replies: Do you not realize that a particular servant of Mine asked you for food but you did not feed him? Didn’t you realize that if you had fed him, you would have found him with Me?
What will make you understand the uphill climb? It is the freeing of a slave. Or feeding on a day of severe hunger the close orphan or the needy person lying in the dust. Then he will become one of those with faith, who urge one another to have patience and urge one another to show compassion and mercy. (Qur’an 90:12-17)
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O Humankind, verily we created you from male and female and made you into nations and tribes so that you may know one another. Indeed, the most honorable of you in the sight of God is the most pious. Verily, God is all-Knowing, all-Aware. (Qur’an 49:13)
O People, your Lord is One, and your father (Ādam) is one. Verily, there is no superiority of an Arab over a non-Arab nor a non-Arab over an Arab. There is no superiority of a white over a black nor a black over a white. Only piety causes one to excel.