海枯石烂不分手
[hăi kū shí làn bù fēn shŏu]
Literally translating as 'the sea dries up, the stones rot, but we don't break up' ('海枯石烂不分手' - hai ku shi lan bu fen shou), this idiom expresses a commitment that lasts forever, no matter what changes may happen. It's about enduring love and fidelity.