天荒地老我还在海枯石烂我还爱
[tiān huāng dì lăo wŏ hái zài hăi kū shí làn wŏ hái ài]
Literally means even when heaven and earth grow old, I will still be here and love you until the seas dry up and rocks decay. Expresses an eternal commitment in love, unswerving through all adversities.