“Never tell a lie when you can tell the truth.”

Source: Light in August

Other

Source: The Kite Runner

Variant: A sign is anything that can be used to tell a lie.
Source: Trattato di semiotica generale (1975); [A Theory of Semiotics] (1976)

1987
Politics
Source: Quotations Collected by Donald Gudehus: Mort Sahl http://www.chara.gsu.edu/~gudehus/Quotations/quotations_rst.html

Source: Harriet the Spy

Source: Memory, Sorrow, and Thorn, To Green Angel Tower (1993), Part 1, Chapter 17, “Bonfire Night” (p. 523).

Source: Culture and Value (1980), p. 44e

Why our future depends on libraries, reading and daydreaming (2013)
Context: We writers – and especially writers for children, but all writers – have an obligation to our readers: it's the obligation to write true things, especially important when we are creating tales of people who do not exist in places that never were – to understand that truth is not in what happens but what it tells us about who we are. Fiction is the lie that tells the truth, after all.