永远不要害怕为诚实、真理和同情而发声，反对不公正、谎言和贪婪。如果全世界的人都这样做，这将改变地球。

This is genuine Faulkner, and its origin is well documented. It comes from
the commencement address he delivered on May 28, 1951 at Fulton Chapel on
the University of Mississippi campus, to the graduating class of University
High School in Oxford, a class that included his daughter Jill, who had
talked her reluctant father into speaking only months after his trip to
Stockholm to accept the Nobel Prize. The four-and-a-half-minute talk was one
of the very few public addresses he ever gave. Faulkner handed his own copy
to the local Oxford Eagle editor, from which it went out on the wire
services, and the text is preserved in the standard collection Essays,
Speeches & Public Letters. Film of Faulkner delivering the speech survives
in the 1952 documentary William Faulkner, and the line can be heard in his
own voice.

The single-sentence version most people share, "If people all over the
world...would do this, it would change the earth," is a compressed excerpt.
The original runs "If you, not just you in this room tonight, but in all the
thousands of other rooms like this one...you will change the earth." The
condensed form is not something Faulkner said, so the full passage is given
here as the quotation of record, with the popular version noted as a
variant.

A stray online claim crediting the British abolitionist William Wilberforce
rests on no source and appears to be simple confusion of two men named
William. There is no documented earlier use and no credible rival author.
The line is authentic Faulkner, spoken and later published.