Who first in human history has promoted equality rights of all people?

(1) The teachings of Buddha, 6th century B.C..

As pointed out by Rajib, while the Principal Teachings of Buddhism may not directly strive for greater equality, but during the time of its inception Buddhism rose as an opposing force to Vedic Brahmanism and certainly held "equality" as one of its primary objectives. So Gautam Buddha makes a case for the pioneers for espousing equality.

Some of the fundamentals of the teachings attributed to Gautama Buddha are:

The Four Noble Truths: that suffering is an ingrained part of existence; that the origin of suffering is craving for sensuality, acquisition of identity, and annihilation; that suffering can be ended; and that following the Noble Eightfold Path is the means to accomplish this;

The Noble Eightfold Path: right view, right intention, right speech, right action, right livelihood, right effort, right mindfulness, and right concentration;

Dependent origination: the mind creates suffering as a natural product of a complex process;

Rejection of the infallibility of accepted scripture: Teachings should not be accepted unless they are borne out by our experience and are praised by the wise.

Anicca (Sanskrit: anitya): That all things that come to be have an end;

Dukkha (Sanskrit: duḥkha): That nothing which comes to be is ultimately satisfying;

Anattā (Sanskrit: anātman): That nothing in the realm of experience can really be said to be "I" or "mine";

Nibbāna (Sanskrit: Nirvāna): It is possible for sentient beings to realize a dimension of awareness which is totally unconstructed and peaceful, and end all suffering due to the mind's interaction with the conditioned world.

(2) Besides, the edicts of Emperor Ashoka , a devout of Buddha from the 3rd Century B.C. also qualify. He is said to have turned a pacifist and converted to Buddhism after witnessing the mass murders in the battle of Kalinga. The edicts describe in detail Ashoka's views on "dhamma", an earnest attempt to solve some of the problems that a complex society faced, besides the extent of proselytism campaigns he carried out.

Dharma is good, but what constitutes Dharma? (It includes) little evil, much good, kindness, generosity, truthfulness and purity. Pilar Edict Nb2 (S. Dharmika)

And noble deeds of Dharma and the practice of Dharma consist of having kindness, generosity, truthfulness, purity, gentleness and goodness increase among the people. Rock Pilar Nb7 (S. Dharmika)

The full translation of the edicts could be found here

(3) Confucius, 6th century B.C., was one of the pioneers of humanism, and his teachings, later structured into Confucianism became an integral part of Chinese thought.

Ugarkina of Lagash, circa the 24th century BCE, is generally credited* as the first effective reformer in recorded history to grant broad legal rights to commoners, the poor and disabled, and elevate many more women into the ranks of the political elite while reigning in secular corruption and abuse of power by wealthy landowners and the priestly class. These reforms and rights are documented on the Liberty Cones of Lagash. The economic reforms are based on those of his predecessor Enmetena, but Ugarkina goes further in guaranteeing the rights of his subjects, and there is evidence of both their positive outcomes, and disastrous consequences (the reactionary military class stood by while the city was conquered.)

(*Criticisms of this claim are typically from the extreme left and right wings of the political spectrum and not supported by available evidence, or worse, confused with Enmetena or other rulers not associated with Lagash.)

Equality can be different: equality before law, equality before God, economic equality, racial/physiological equality, sexual equality etc etc etc.

Neither Judaism nor Christianity nor traditional classical religion provided for universal equality.

Judaism

• permits slavery (inequality before law)

• provides that Jews are the chosen people, prefers monotheistic non-Jews to polytheistic, restricts women's rights to participate in the service and visit the temple, provides for a priest caste (levites), restricts rights of the wounded to become priests, prefers a chosen dynasty of kings (those who descended from David), alleges that blacks were punished by the God for their sins with black color of their skin. (inequality before God, sexual inequality, racial inequality)

Christianity

• permits slavery, although discourages it, permits hereditary dynasties (inequality before law)
• provides that Christians are preferred to non-Christians (inequality before God)
• restricts women's rights to become priests (sexual inequality)

Similar lists one can compile about any religion, doctrine and ideology.

(I have limits on how many references I can add. I will bold important terms that have useful Wikipedia pages) The UN Universal Declaration of Human Rights represents the first global expression of rights to which all human beings are inherently entitled. It was signed in 1948 by the UN General Assembly. It elaborates on the ideas of: 1. US President Franklin D. Roosevelt that all people have "Four Freedoms": freedom of speech, freedom of religion, freedom from fear and freedom from want 2. The original United Nations Charter which "committed all member states to promote universal respect for, and observance of, human rights and fundamental freedoms for all without distinction as to race, sex, language, or religion" 3. "Code Napoléon" principles of dignity, liberty, equality and brotherhood.

The earliest example of a person to promote universal human rights is Sir Thomas More in the seminal work, "Utopia," published in 1516. Utopia was a fictional republic without landed gentry or lords, but rather with an elected parliament. The people have freedom of religion and common property (equality in wealth). Honors are bestowed for virtue, not for wealth or status, such as being the elected prince. The legal system is simplified so that everyone can have equal justice. Slavery, or forced labor, is disallowed except as a harsh criminal sentence and many rules are enforced to protect the criminals. The Utopians use the j*ust war theory* and avoid brutality in warfare. Women are allowed to be priests, in the military, and commonly work in the economy outside the home. Divorce is allowed in some circumstances, no arranged marriages and they have some sexual freedom before marriage.

More was a *Christian Humanist* who lived from 1478–1535, which places him decades to nearly a century to many writers of the Enlightenment on the subject of human rights, such as Voltaire. He was close friends with Erasmus, who is credited with laying the foundations for the philosophy of religious tolerance in Europe due to his close relationship with Martin Luther. More was considered the most influential philosopher in England at the time he was martyred by Henry XIII, ironically in some ways, for refusing to endorse his divorce.

If I were to name a non-sectarian document, I would cite the Hammurabi Code dates to somewhere in the early 18th century BC. It has the basic, "presumed innocent" idea — something we, in the United States, hold sacrosanct.

After some research i have also found this verse (Galatians 3:28, NIV) in New Testament:

There is neither Jew nor Gentile, neither slave nor free, nor is there male and female, for you are all one in Christ Jesus.

It might be younger than Hammurabi Code or story of Noah but in my opinion it describes freedom in little bit wider aspect so it is still worth mentioning.