All is fair in love and war
katika mapenzi na vita kila kitu ni halali
In Swahili Katika mapenzi na vita, kila kitu ni halali.
This idiom is used in Swahili to express that the rules are different in love and war.
Example
"Alifanya kila kitu ili kumpata, katika mapenzi na vita, kila kitu ni halali."
