“My country is the world, and my religion is to do good.”

Part 2.7 Chapter V. Ways and means of improving the condition of Europe, interspersed with miscellaneous observations
Source: 1790s, Rights of Man, Part 2 (1792)
Context: I speak an open and disinterested language, dictated by no passion but that of humanity. To me, who have not only refused offers, because I thought them improper, but have declined rewards I might with reputation have accepted, it is no wonder that meanness and imposition appear disgustful. Independence is my happiness, and I view things as they are, without regard to place or person; my country is the world, and my religion is to do good.

The earliest found citation is in K.O. Meinsma, Spinoza en zijn kring. Historisch-kritische studiën over Hollandsche vrijgeesten (Martinus Nijhoff, 's-Gravenhage, 1896). This influential study was translated in French and German, but not in English. In the original Dutch context it seems as though this is not a quote from Huygens, but a characterisation by the author (Meinsma) of what 'could haven been' Huygens' devise.
In Cosmos: A Personal Voyage (Episode 6) from 1980 it is phrased The world is my country, science my religion.
Also in The Making of Modern Europe, 1648-1780 (1985) by Geoffrey Treasure, p. 474, it is declared that this was Huygens' "motto" — but this seems very similar to the much more famous and long attested declaration of Thomas Paine in Rights of Man (1791): "My country is the world, and my religion is to do good" which has long been paraphrased "The world is my country, and to do good is my religion."
Disputed

Quoted in 3:439 Herndon&#x27;s Lincoln (1890), p. 439 http://books.google.com/books?id=rywOAAAAIAAJ&amp;pg=PA439&amp;dq=%22when+i+do+good+i+feel+good%22: Inasmuch as he was so often a candidate for public office Mr. Lincoln said as little about his religious code as possible, especially if he failed to coincide with the orthodox world. In illustration of his religious code I once heard him say that it was like that of an old man named Glenn, in Indiana, whom he heard speak at a church meeting, and who said: &quot;When I do good I feel good, when I do bad I feel bad, and that&#x27;s my religion.&quot; <br class="br">Posthumous attributions

quote published in Pakistan Studies Journal Pakistaniaat ( Vol. 3 No.2 of 2011 http://pakistaniaat.org/index.php/pak/article/view/129/129/). Retrieved on July 20, 2016

The Beatles Anthology (2000)

The Beaux’ Stratagem (1707), Act iii. Sc. 2. Compare: "Leaving his country for his country’s sake", Fitz-Geffrey, The Life and Death of Sir Francis Drake (1596), stanza 213.; "True patriots all; for, be it understood, / We left our country for our country’s good", George Barrington, Prologue written for the opening of the Play-house at New South Wales, Jan. 16, 1796. New South Wales, p. 152.

Radio Times April 2007

On the tax charges against him, in a speech at Foley Square in New York City (22 October 1981); published in a full page advertisement in the The New York Times (5 November 1981), as quoted in US Court of Appeals document U.S. v. Sun Myung Moon 718 F.2d 1210 (1983)

Quoted in "Sunil Dutt — film star, peace activist, secularist, politician extraordinary" in The Hindu.
We all are one, whichever religion we belong to