“The literate man is a sucker for propaganda... You cannot propagandize a native. You can sell him rum and trinkets, but you cannot sell him ideas.”

Attributed to Marx (possibly in jest) in W. C. Privy's Original Bathroom Companion (2003).
Misattributed

Source: The Greening of America (1970), Chapter VII : "It's Just Like Living", p. 162

In Star Science Fiction 5, edited by Frederik Pohl, p. 53
Short fiction, Company Store (1959)

Variant: When you sell a man a book you don’t sell him just twelve ounces of paper and ink and glue - you sell him a whole new life. Love and friendship and humour and ships at sea by night - there’s all heaven and earth in a book, a real book I mean.
Source: Parnassus on Wheels

As quoted in How to Win Friends and Influence People (1935) by Dale Carnegie, p. 117; also paraphrased as "You cannot teach a man anything, you can only help him to find it for himself." Attributions are found as early as 1882.
Attributed
Source: Google Books link https://books.google.com/books?id=h70_AQAAMAAJ&pg=PA476&dq=You+cannot+teach+a+man+anything;+you+can+only+help+him+find+it+within+himself&hl=en&sa=X&ved=0CB0Q6AEwAGoVChMI39Gmss_gyAIVRNRjCh1Q2wGN#v=onepage&q=%22You%20cannot%20teach%22&f=false

Source: The Languages of Pao (1958), Chapter 8 (p. 64)

To a raiding band, after protecting an ambushed white soldier with her shawl, as quoted in Eagle Woman Who All Look At, 2010, South Dakota Hall of Fame – Champions of Excellence, 2019-08-15 http://sdexcellence.org/Eagle_Woman_Who_All_Look_At_2010,

Alternatively, "This Man belongs to me now! You cannot mutilate him nor touch him!" as quoted in [Joseph Agonito, Brave Hearts: Indian Women of the Plains, https://books.google.com/books?id=QZ7RDAAAQBAJ, 1 October 2016, TwoDot, 978-1-4930-1906-9]

Source: Double Star

Source: Atlas Shrugged