“Human work must be done thoroughly and honourably because we are now men; whether we ever expect to be angels, or ever were slugs, being practically no matter.”

Source: The Wars

Preface; Extermination
Ignoring the satirical elements of Shaw's rhetoric, and that he is presenting many arguments of sometimes questionable sincerity for the "humane" execution of criminals, the last sentence here has sometimes been misquoted as if it as part of an argument for exterminations for the sake of eugenics, by preceding it with a selected portion of a statement later in the essay: "If we desire a certain type of civilization, we must exterminate the sort of people who do not fit into it … Extermination must be put on a scientific basis if it is ever to be carried out humanely and apologetically as well as thoroughly".
1930s, On the Rocks (1933)
Context: In this play a reference is made by a Chief of Police to the political necessity for killing people: a necessity so distressing to the statesmen and so terrifying to the common citizen that nobody except myself (as far as I know) has ventured to examine it directly on its own merits, although every Government is obliged to practise it on a scale varying from the execution of a single murderer to the slaughter of millions of quite innocent persons. Whilst assenting to these proceedings, and even acclaiming and celebrating them, we dare not tell ourselves what we are doing or why we are doing it; and so we call it justice or capital punishment or our duty to king and country or any other convenient verbal whitewash for what we instinctively recoil from as from a dirty job. These childish evasions are revolting. We must strip off the whitewash and find out what is really beneath it. Extermination must be put on a scientific basis if it is ever to be carried out humanely and apologetically as well as thoroughly.

Address to fleet officers (August 11, 1917), quoted in Joseph P. Tumulty, Woodrow Wilson As I Know Him (1921), p. 297 https://books.google.com/books?id=f3xw1nfcn14C&vq=%22Nothing%20was%20ever%22&pg=PA297#v=onepage&q&f=false
1910s

Credo (1901)
Context: I believe in the Motherhood of God.
I believe in the Blessed Trinity of Father, Mother and Child.
I believe that God is here, and that we are as near Him now as ever we shall be.
I do not believe He started this world a-going and went away and left it to run by itself.
I believe in the sacredness of the human body, this transient dwelling place of a living soul, And so I deem it the duty of every man and every woman to keep his or her body beautiful through right thinking and right living.
I believe that the love of man for woman, and the love of woman for man is holy; And that this love in all its promptings is as much an emanation of the Divine Spirit as man's love for God, or the most daring hazards of the human mind.
I believe in salvation through economic, social, and spiritual freedom.
I believe John Ruskin, William Morris, Henry Thoreau, Walt Whitman, and Leo Tolstoy to be Prophets of God, who should rank in mental reach and spiritual insight with Elijah, Hosea, Ezekiel, and Isaiah.
I believe that men are inspired to-day as much as ever men were.
I believe we are now living in Eternity as much as ever we shall.
I believe that the best way to prepare for a Future Life is to be kind, live one day at a time, and do the work you can do best, doing it as well as you can.
I believe we should remember the Week-day, to keep it holy.
I believe there is no devil but fear.
I believe that no one can harm you but yourself.
I believe in my own divinity — and yours.
I believe that we are all sons of God, and it doth not yet appear what we shall be.
I believe the only way we can reach the Kingdom of Heaven is to have the Kingdom of Heaven in our hearts.
I believe in every man minding his own business.
I believe in sunshine, fresh air, friendship, calm sleep, beautiful thoughts.
I believe in the paradox of success through failure.
I believe in the purifying process of sorrow, and I believe that death is a manifestation of life.
I believe the Universe is planned for good.
I believe it is possible that I shall make other creeds, and change this one, or add to it, from time to time, as new light may come to me.

Fragments of Melissus's On Nature, Fragment 1

If women are to have the same duties as men, they must have the same nurture and education. — Plato, The Republic, Book V, trans. Benjamin Jowett, third edition, Oxford University Press, 1892 http://oll.libertyfund.org/Home3/HTML.php?recordID=0345#hd_lf131.3.head.017
Misattributed
Variant: So if we are going to use men and women for the same purposes, they must be taught the same things. The Republic, trans. Desmond Lee [Penguin Classics, 2003, ISBN 0-140-449140-0], p. 161
Variant: Then if we are to use the women for the same things as the men, we must teach them the same things. The Republic, trans. W. H. D. Rouse [Signet Classic, 1999, ISBN 0-451-52745-3], p. 249

After the Funeral (1953)

Source: Initiation, The Perfecting of Man (1923)

1990s, The Party of Lincoln vs. The Party of Bureaucrats (1996)
Context: Suddenly, however, remedies for something called 'racism' became the order of the day. The word itself, like 'sexism', is of recent coinage and will not be found in any older dictionaries. The civil rights movement, premised upon individual rights, suddenly became the black power movement, premised upon group rights. 'Affirmative action' became a euphemism for the baldest kind of racial discrimination. That whites had long enjoyed preference over blacks was now taken to be a justification for blacks having preference over whites. What was lost sight of was that the evil of the past, whether of slavery or of Jim Crow, was evil not because it was done by whites to blacks, but because it was done by some human beings to other human beings. The purpose of the law was to end evil acts, not continue them in the guise of 'affirmative action'.