Tawhid as an outlook of human existence, implies the equality and unity of all human beings in their relation with God. He is the Lord of all human beings. No one has any special relationship with Him denied to others. He is not the God of a specific community or a particular tribe which may enjoy special privileges over other com­munities and tribes through His patronage; all are equal before Him. If He makes any distinctions, it is on the basis of struggle and effort for attainment of piety and pursuance of His path; something which is open to all human beings, and which alone can promise man's edification
And they say, `God has taken to Him a son'. Glory be to Him! Nay, to Him belongs all that is in the heavens and the earth; all obey His will. (2:116)
And:
And whosoever does deeds of righteousness, being a believer, no un-thankful­ness shall befall his endeavour; We Ourselves write down for him. (21:94)
And also
O mankind, We have created you male and female, and appointed you nations and tribes, that you may know one another. Surely the noblest among you in the sight of God is the most God-fearing of you ....(49:13)
Tawhid also bears the notion of homogeneity, equality and unity of human origin. Humanness is the single basic element ingrained in the nature of all human individuals. Human beings associated with the different social strata are neither the creations of different gods so that there can exist any disparity in their essential nature, giving rise to insuperable barriers amongst them; nor it is that the god of the upper classes of society is more powerful than that of the lower classes. All are the creation of one and the same God, and all are uniform in their fundamental essence.
O mankind, fear your Lord, who created you of a single soul ....(4:1)
Tawhid also means equality and homogeneity in human potentiali­ties of development and perfection; since everyone of us is endowed with the same type of human essence and constitution, no one is incapable of traversing the straight path of spiritual exaltation and progress. Accordingly, the Divine call is a general call addressed to all humanity in general, not to any specific race, class or individual-although there is the possibility that differences of social atmospheres and conditions may subject individuals to varying effects. However, these negative factors by themselves can never determine human behaviour, or turn men permanently into saints or devils, or deprive them of the capacity of free choice. Addressing the Prophet (S), the Quran says:
We have sent thee not, except to mankind entire (not to any specific com­munity) .... (34:28)
....And We have sent thee as a messenger to mankind .... (4:79)
The Quran also says in this context:
O men, proof has come to you from your Lord, We have sent down to you a manifest light. As for those who believe in God, and hold fast to Him He will surely admit them to mercy from Him, and bounty, and will guide them to Him on a straight path. (4:174-175)
Tawhid also implies the liberation and freedom of mankind from bondage and servitude of multiple varieties of non-Gods; in other words, it stands for the necessity of exclusive servitude to God. The principle of Tawhid negates the mode of living in subjection (intellectual, cultural, economic or political) to creatures, the various forms of non-­Gods, whose service takes the place of the worship of God, or degrades it to secondary significance. The doctrine of Tawhid considers man as a servant of God, liberating him from the bondage and servility to any thing, individual, or system which takes the central place of God in the scheme of life.
Thus the principle of Tawhid implies submission to Divine autho­rity, and negation of every kind of domination by non-God in every form and shape:
Sovereignty belongs only to God; He has commanded that you shall not serve any but Him. That is the right religion .... (12:40)
Thy Lord has decreed that you shall worship none but Him ....(17:23)
On this basis, Tawhid also implies the inherent worth and value of the human being. The human being is more exalted and worthy than that he should pay obeisance to anything but God. It is the Absolute Being, the Absolute Beauty and Perfection alone, which deserves to engage man's love and adoration. This emphasis on the exaltation of the object of worship itself implies exaltation of the station of the wor­shipper, i.e. the human being. Nothing except the Perfect Being is worthy of man's praise and adoration. All the idols, animate or inani­mate, which have imposed themselves on the hearts and minds of human beings, and have forcefully encroached upon the realm of the Almighty's authority over human existence, are nothing but filth and abomination, which defiles human being's natural purity and grace, bringing him degradation and disgrace. In order that man should reclaim his exalted station, it is essential that he exterminates the un­holy influence of the idols from his life. No materialistic humanism has ever succeeded in bringing a like profundity and elegance to the discussion of human worthiness and greatness to the extent of Tawhid:
....And eschew the abomination of idols, and eschew the speaking of falsehood being men pure of faith unto God, not associating with Him anything; for whosoever associates with God anything, is as though he has fallen from heaven and the birds snatch him away, or the wind sweeps him headlong into a place far away. (22:30-31)
And:
Set not up with God another god, or thou wilt sit condemned and forsaken. (17:22)
And also:
Set not up with God another god, or thou wilt be cast into Gehanna, re­proached and rejected. (17:39)
The principle of Tawhid also includes the notions of unity and uniformity in the field of human existence. Human existence is a synthesis of subjective and objective reality, thought and action. If any one of these two, or even a part of each, falls under the influence of anti-God forces, it results in the formation of a split personality. The faith in God is mixed with idolatrous tendencies. In such conditions, man, like a compass needle influenced by an alien magnetic field, loses his true orientation; that is, he deviates from the straight path of God, the Pole of righteous human orientation-a deviation which is alien to the human nature:
....What, do you believe in part of the Book, and disbelieve in part? What shall be the recompense of those of you who do that, but degradation in the present life, and on the Day of Resurrection to be returned unto the most terrible chastisement? ....(2:85)
The principle of Tawhid also implies necessity of man's harmony with the world around him. The vast realm of the universe, a scene of innumerable actions and reactions among various laws which deter­mine completely even the most insignificant phenomena in it, is a unit governed by coherent and harmonious laws-a coherence and harmony of which the human world is also a part. Although the human world is subject, in addition to the general laws of Nature, to a particular set of laws special to itself, yet it is always in harmony with other laws governing the rest of phenomena beyond it. But man, unlike his other fellow creatures who are bound to tread the path of Nature without any choice whatsoever, is endowed with the power of free will and free choice. He, unlike them, carries the burden of freedom together with the obligation to harmonize his life with the rest of Nature-a harmony which is also the path of his exaltation and progress. This means that he always carries within himself the alternative to deviate from the course of nature:
....so let whosoever will believe, and let whosoever will disbelieve ....(18:29)
The principle of Tawhid calls man to follow the path of nature, which is being followed by the whole universe. It seeks to unite him in his search with the vast domain of being, and strives to create an absolute unity and solidarity between the universe and man, who is its most essential partner in the realm of existence:
What, do they desire another religion than God's, and to Him has surrendered whoso in the heavens and the earth, willingly or unwillingly, and to Him they shall be returned? (3:83)
Hast thou not seen how to God prostrate all who are in the heavens and all who are in the earth, the sun and the moon, the stars and the mountains, the trees and the beasts, and many of mankind? ....(22:18)

Source: Selected Chapter from Al-Tawhid and Its Social Implications by Ayatullah Sayyed Ali Khamenei