兩虎相爭，必有一傷 [两－－争－－－－伤]

Jyutping loeng5 fu2 soeng1 zang1 , bit1 jau5 jat1 soeng1
Pinyin liǎng hǔ xiāng zhēng , bì yǒu yī shāng

Definitions (CC-CEDICT)
  1. if two tigers fight, one will get injured (idiom)
  2. if you start a war, someone is bound to get hurt