媳妇可以长相依马子不能代替妻
[xí fù kĕ yĭ zhăng xiāng yī mă zi bù néng dài tì qī]
'Xifu ke yi chang xiang yi ma zi bu neng dai ti qi'. In China's slang, 'xifu' and 'qi' refer to wife or husband's wife, and 'ma zi', originally from gangster slang now has become widely used referring to girlfriend. So it implies the feeling towards a legal wife that no 'girlfriends' could replace her, indicating cherishment to the one who can be by your side forever