我结婚的时候你是伴娘你结婚的时候我是伴娘
[wŏ jié hūn de shí hòu nĭ shì bàn niáng nĭ jié hūn de shí hòu wŏ shì bàn niáng]
A mutual agreement of friendship between two close friends who promise to be each other’s bridesmaids when they get married. This shows a deep bond of sisterhood and lifelong commitment to supporting one another.