He thought he could hide it, but if you don't want others to know, you must not do it.
Tips
history
The first half of a well-known proverb pair: 若要人不知，除非己莫为 - 'If you want others not to know, then you yourself must not do it.' The saying echoes an earlier formulation in a memorial attributed to the Han scholar Mei Sheng (枚乘): 欲人勿闻，莫若勿言；欲人勿知，莫若勿为. The popular modern rhyme became proverbial through ballads and vernacular fiction.
usage
Always used with the closing line 除非己莫为. Common in proverbs about honesty and consequences - favored in parental lectures and anti-corruption editorials.
