At the opening of the Eighth Party Congress in September 1956, Mao Zedong said: “An open mind helps people progress. Conceit makes people fall behind. We should always remember this truth.”
The sentence (虚心使人进步，骄傲使人落后) became a poster slogan. A 1996 poster in a series called “Famous People, Famous Words” carried it under Mao’s name.