三歲定八十

三岁定八十
sānsuìdìngbāshí

the character of a person is already formed at a young age

Wiktionary

Entry Composition

=1 三 Sān surname San
=1 三 sān
  1. three
  2. 3
2 歲 suì
  1. classifier for years (of age)
  2. year
  3. year (of crop harvests)
3 定 dìng
  1. to fix; to set; to make definite
  2. to subscribe to (a newspaper etc); to book (tickets etc); to order (goods etc)
  3. to congeal; to coagulate
  4. (literary) definitely
4 八十 bāshí
  1. eighty
  2. 80