二虎相鬥，必有一傷 [－－－斗－－－－伤]

Jyutping
Pinyin èr hǔ xiāng dòu , bì yǒu yī shāng

Definitions (CC-CEDICT)
  1. lit. when two tigers fight, one is sure to be wounded (idiom)
  2. fig. if it comes to a fight, someone will get hurt