不打不相识 bù dǎ bù xiāngshí

[Out of blows friendship grows;It takes a fight for people to get know each other] 谓经过交手,相互了解,能更好地结交、相处

上次闹了点误会,还记在心里?不打不相识嘛。来,里面坐。——陆文夫《不平者》