“Friends front in front of me
Fuckin' wannabes
In your ear
But they don't know Eamon”

Young British Soldier, Stanza 9.
Barrack-Room Ballads (1892, 1896)

I'm Supposed to Die Tonight
Song lyrics, The Massacre (2005)

Also found in variants such as "A true friend stabs you in the front".
The earliest known example of this quote comes from Walter Winchell's syndicated newspaper column in mid-January 1955: 'On Broadway, cynically reports Jimmy Nelson, "a true friend is one who stabs you in the front"'
The earliest version of this quote found in Google Books is from 1958, where the quote "A true friend is one who stabs you in the front" is attributed to actor Steve Dunne https://books.google.com/books?id=MF5-AAAAMAAJ&q=friend+%22stabs+you+in+the+front%22&dq=friend+%22stabs+you+in+the+front%22&hl=en&sa=X&ved=0ahUKEwig2JCRnKrMAhUC42MKHaNzCGsQ6AEIHDAA.
In 1981, a similar quote: "He is a fine friend. He stabs you in the front" was attributed to Hollywood writer and producer Leonard Levinson https://books.google.com/books?id=Xbe8zbfuVLgC&q=friend+%22stabs+you+in+the+front%22&dq=friend+%22stabs+you+in+the+front%22&hl=en&sa=X&ved=0ahUKEwjMjOrQnKrMAhVL2GMKHcQQDSgQ6AEIHTAA.
In 1984, an article in Ms. Magazine https://books.google.com/books?id=sfIbAQAAMAAJ&q=friend+%22stabs+you+in+the+front%22&dq=friend+%22stabs+you+in+the+front%22&hl=en&sa=X&ved=0ahUKEwjMjOrQnKrMAhVL2GMKHcQQDSgQ6AEIJzAC stated that "the Hollywood definition of a friend" was "someone who stabs you in the front".
The earliest attribution to Oscar Wilde was from 1989 https://books.google.com/books?id=CnQJAAAAIAAJ&q=friend+%22stabs+you+in+the+front%22+wilde&dq=friend+%22stabs+you+in+the+front%22+wilde&hl=en&sa=X&ved=0ahUKEwj2oqLfnKrMAhVG52MKHXdPANkQ6AEIJTAC: "A good friend is one who stabs you in the front". No source was given.
Disputed
Variant: A good friend will always stab you in the front.
Source: e.g. "Broadway and Elsewhere" https://www.newspapers.com/newspage/3706522/, Pharos-Tribune (Logansport, IN), 1955-01-16, p. 4

Letter to Oskar Pollak (8 November 1903); cited from Briefe, 1902-1924 (1958) edited by [Max Brod]], p. 27<!-- New York: Schocken --> ; translation from Franz Kafka, Representative Man (1991) by Frederick R. Karl, p. 98 <!-- New York: Ticknor & Fields -->
Context: We are as forlorn as children lost in the woods. When you stand in front of me and look at me, what do you know of the griefs that are in me and what do I know of yours? And if I were to cast myself down before you and weep and tell you, what more would you know about me than you know about Hell when someone tells you it is hot and dreadful? For that reason alone we human beings ought to stand before one another as reverently, as reflectively, as lovingly, as we would before the entrance to Hell.

Original: (it) Il rispetto che i veri amici hanno nei tuoi confronti non permetterà mai loro di essere dietro o davanti al tuo percorso di vita, ma sempre al tuo fianco.
Source: prevale.net

Extended tweet at TwitLonger (14 August 2010)
Twitter tweets

Source: Naruto, Band 11

Source: The Secret Scripture

Widely attributed, but likely apocryphal. https://quoteinvestigator.com/2015/08/23/friend/ Researchers have searched for this quote unsuccessfully in Camus' extant works.
Disputed