無巧不成書 [无－－－书]

Jyutping mou4 kiu2 bat1 sing4 syu1
Pinyin wú qiǎo bù chéng shū

Definitions (CC-CEDICT)
  1. curious coincidence
Definitions (Wiktionary)
  1. phrase, idiomatic
    to be very coincidental; to be very fortuitous