《礼记·中庸》
没有什么比隐蔽的东西更能说明问题，没有什么比细微的小事更能显露本相。所以君子对自己独处时的行为和思想特别谨慎。
莫见乎隐，莫显乎微，故君子慎其独也。
Nothing is more expressive than what is hidden, and there is nothing that reveals character more than the most minute details. Therefore, the gentleman is especially cautious about his conduct and thoughts when he is alone.