不言自明

bùyánzìmíng
self-evident; needing no explanation (idiom)

CEDICT

to be self-evident; to go without saying

Wiktionary

Entry Composition

1 不 bù
  1. no; not so
  2. (bound form) not; un-
2 言 yán
  1. words
  2. speech
  3. to say
  4. to talk
3 自明 zìmíng to be self-evident