“Unjust Cause: This art is worth more than ten thousand staters, that one should choose the worse cause, and nevertheless be victorious.”
tr. Hickie 1853, vol. 1, Perseus http://www.perseus.tufts.edu/hopper/text.jsp?doc=Aristoph.+Cl.+1041
Clouds (423 BC)
Help us to complete the source, original and additional information
Aristophanés 56
Athenian playwright of Old Comedy -448–-386 BCRelated quotes

“One loyal friend is worth ten thousand relatives.”

Source: The Exposition of 1851: Views Of The Industry, The Science, and the Government Of England, 1851, p. xii-xiii; Cited in: Samuel Smiles Industrial biography; iron-workers and tool-makers http://books.google.com/books?id=5trBcaXuazgC&pg=PA104, (1864) p. 104

“Lost causes are the only ones worth fighting for.”
This quote is from Ethel Lina White's The Wheel Spins (1936). It was popularized in the film Mr. Smith Goes to Washington (1939). In this film a similar line was spoken by "Jefferson Smith".
Misattributed

“Every cause produces more than one effect.”
On Progress: Its Law and Cause
Essays on Education (1861)
“Lost causes are the only causes worth fighting for.”
The Wheel Spins (1932), p 270.
A variation of this quote also appears in the film Mr. Smith Goes to Washington

“A well-fought defeat is worth more than a casual victory.”
Una derrota peleada vale más que una victoria casual.
100 Masones Su Palabra (2010)

“There are causes worth dying for, but none worth killing for.”
Widely attributed to Camus on the internet, the earliest attribution of such a statement to him yet located is an unsourced citation in Quotations from the Wayside (1999) by Brenda Wong: "Many things are worth dying for, but none worth killing for." The earliest occurrence yet located of such a statement, by anyone, is one by Albert Dietrich in a 31 January 1943 letter to his conscientious objector status Hearing Officer, reported in Army GI, Pacifist CO : The World War II Letters of Frank and Albert Dietrich (2005) https://books.google.co.uk/books?id=3o4JN_C69VwC edited by Scott H. Bennett: "There are perhaps many causes worth dying for, but to me, certainly, there are none worth killing for."
Prior to the attribution to Camus, the most widely publicized occurrence of such an expression was probably in the song "Too Long A Soldier" https://www.youtube.com/watch?v=YoQcU1ecPOc by Neil Giraldo and Myron Grombacher, sung by Pat Benatar on her album Wide Awake In Dreamland (1988): "I've seen so much worth dying for, so little worth killing over."
Misattributed