The "Unity" is the basis of Islamic theology. and therefore "Unity" is the ground of its philosophy of society. All humanity is one; a great unit. Its individuals are members of one society incorporate, which is so comprehensive that it includes all differences within its oneness. The many find within the one that brotherhood, affection, friendliness and human blood-relationship which is of the essence. Hence distinctions do not become differences - not colour, nor culture, nor class, nor custom, nor conversational idiom. Mutual respect as fellow-humans in pursuit of the common good is the rule throughout the world-wide society of Islam, without superiority or inferiority, since all mankind were created in one human soul to start with, from whom man and woman, black and white, poor and rich, civilised and savage, all evolve, sharing one common humanity Truly "God made of one flesh all the nations upon earth it haply they may feel after Him and find Him."
So it is written (Qur'an: Sura IV Nisa'a-"The Women" 1st verse). "Reverence God Who created you all from one person", leaving no room for nationalistic divisions. Differences in skin and tongue are merely tokens of the Creator's power. They call on men to study the Holy Will and Might of Him Who from one elemental root created so many variations of colour countenance and conversation : as it is written (Qur'an: Sura XXX "Rome" verse 21)"Signs of His Power are His creation of heaven and of earth, and the varieties of tongues and skins; in all of which are sermons for the wise."
It is further written (Qur'an : Sura II, Baqara -"The Heifer" verse 213): "Mankind was one single nation. Then we sent messengers to them to give them glad tidings and warnings; and with them we sent the Book in truth to judge between people in matters wherein they differed . . . and God by His grace guided believers to the common truth on points about which they differed; for God guides whom He will onto a path that is straight." This verse reveals that in the beginning mankind was one single nation without differences or splits or conflicts but enjoying unity, cooperation and harmony.
The martyred Imam Ali left us the priceless legacy of the Nahj-ul-Balaghe, amongst which is his historic address to Malek_iyAshtar in which he expresses this truth as follows: "Make thine heart a throne of mercy towards thy people. Show them perfect love and care. Never treat them as a ravening beast that tears and rends their properties and their persons. For they are in one of two groups. Either they are thy brothers in the Faith- or they are thy fellow-human beings of one flesh with thine own." This broad view embraces all races, all cultures, all tongues.
Unity and union amongst individuals will subsist under the aegis of unity of thought and spirit, oneness of conviction and aim; nor can any unity obtain save under that orderliness. Should a society fall into division of thought and conviction, its bonds of affection will be loosened: and. when adversity arises, material needs will increase differences, conflicts and tensions. That is why the strongest tie of unity amongst nations is the religious bond.
It is in this bond of union that Islam has brought people and peoples together, freeing them from the trammels of division and difference, and calling them to establish the bases of accord and agreement in a society of brotherhood which is the natural state of man.
Islam treats mankind as one great family of brothers and sisters. In the human family the relationship of father and child is a stronger bond than that of brotherhood. But the qualities of respect and of difference of age deprive the father-child relationship of full equality. That is why it is brotherhood which Islam exalts as the expression of that perfect and heartfelt affection which should reign within the human family. It should reign on the surface and in the depths. Brotherhood is therefore the Qur'an's call. The sublimest levels of love and the most sincere of friendships are those which arise between Muslims. They are called brothers because of their brotherhood, because of the existence of the fact of this most tender and beautiful of manifestations of equality; it is not the command to be brothers which called the fact into existence. The command was uttered, but the natural upwelling of the spirit engendered by that surrender (tasleem) to God (which Islam is) issues in brotherhood.
This brotherhood is deeper and higher than mere natural brotherliness, for it is the unity of a shared aim, the unity of shared convictions, the unity of joint beliefs, the unity of hearts.
It is written (Qur'an: Sura XLIX, Hujurat-"The Inner Apartments" verse 10): "Believers are a single brotherhood. Make peace amongst your brothers and fear God that ye may receive mercy."
The Prophet decreed: "The members of the assembly of the believers are by love and affection one body, and any limb of that which is pained causes all the other limbs to suffer in sympathy. If any individual Muslim falls into a painful situation all the other members of the community must run to his help and share in his sorrow." (Safeenatu-l-Behar, Vol. I, p.13.)
source : rafed.net