文如其人

wénrúqírén
the writing style mirrors the writer (idiom)

CEDICT

like author, like book

Wiktionary

文章的风格充分反映出作者的思想、为人。

重編國語辭典

Entry Composition

1 文 wén
  1. language
  2. culture
  3. writing
  4. formal
  5. literary
  6. gentle
  7. (old) classifier for coins
  8. Kangxi radical 67
2 如 rú
  1. as
  2. as if
  3. such as
3 其人 qírén that person; the person in question