If you don't want others to know about something, don't do it in the first place. What is done in secret will eventually be exposed.
小明以为自己偷偷拿走了邻居的玩具没有人知道，但他忘了若要不知，除非莫为，很快就被发现了
Xiao Ming thought no one knew he secretly took his neighbor's toy, but he forgot that if you don't want others to know, don't do it, and he was soon discovered.
Next Idiom