To understand without needing an explanation
This effectively means "it goes without saying," and it's generally used the same way as in English
Neutral
It goes without saying
不言而谕 (bù yán ér yù)
This is an HSK chengyu
《孟子》(Mèng Zǐ), a classic Confucian work written by the philosopher of the same name. The work is often known in English as "The Book of Mencius."
This chengyu comes from a line in the work listed in the "Origin" section above