“Soon, they began to insist that inasmuch as Colour, which was a second Nature, had destroyed the need of aristocratic distinctions, the Law should follow in the same path, and that henceforth all individuals and all classes should be recognized as absolutely equal and entitled to equal rights.”

Marriage protest (1855)

Source: Utilitarianism (1861), Ch. 5

Source: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" from a memoir, published (1817).

Source: A Theory of Justice (1971; 1975; 1999), Chapter II, Section 12, pg. 73

Cambridge 1995, p. 170, 171
The Ego and Its Own (1844)

Speech at the Civil Rights Mass-Meeting Held at Lincoln Hall (22 October 1883), as quoted in The Life and Times of Frederick Douglass https://archive.org/stream/lifetimesoffrede1881doug/lifetimesoffrede1881doug_djvu.txt (1881).
1880s, Speech at the Civil Rights Mass Meeting (1883)

Dune Genesis (1980)
Context: In the beginning I was just as ready as anyone to fall into step, to seek out the guilty and to punish the sinners, even to become a leader. Nothing, I felt, would give me more gratification than riding the steed of yellow journalism into crusade, doing the book that would right the old wrongs.
Reevaluation raised haunting questions. I now believe that evolution, or deevolution, never ends short of death, that no society has ever achieved an absolute pinnacle, that all humans are not created equal. In fact, I believe attempts to create some abstract equalization create a morass of injustices that rebound on the equalizers. Equal justice and equal opportunity are ideals we should seek, but we should recognize that humans administer the ideals and that humans do not have equal ability.

The Rights of the Colonists (1772)

1850s, Speech on the Dred Scott Decision (1857)
Context: I think the authors of that notable instrument intended to include all men, but they did not intend to declare all men equal in all respects. They did not mean to say all were equal in color, size, intellect, moral developments, or social capacity. They defined with tolerable distinctness, in what respects they did consider all men created equal; equal in "certain inalienable rights, among which are life, liberty, and the pursuit of happiness." This they said, and this meant. They did not mean to assert the obvious untruth, that all were then actually enjoying that equality, nor yet, that they were about to confer it immediately upon them. In fact they had no power to confer such a boon. They meant simply to declare the right, so that the enforcement of it might follow as fast as circumstances should permit. They meant to set up a standard maxim for free society, which should be familiar to all, and revered by all; constantly looked to, constantly labored for, and even though never perfectly attained, constantly approximated, and thereby constantly spreading and deepening its influence, and augmenting the happiness and value of life to all people of all colors everywhere. The assertion that "all men are created equal" was of no practical use in effecting our separation from Great Britain; and it was placed in the Declaration, nor for that, but for future use. Its authors meant it to be, thank God, it is now proving itself, a stumbling block to those who in after times might seek to turn a free people back into the hateful paths of despotism. They knew the proneness of prosperity to breed tyrants, and they meant when such should re-appear in this fair land and commence their vocation they should find left for them at least one hard nut to crack. I have now briefly expressed my view of the meaning and objects of that part of the Declaration of Independence which declares that "all men are created equal".