陪你到世界尽头陪你到白发苍苍
[péi nĭ dào shì jiè jĭn tóu péi nĭ dào bái fā cāng cāng]
Expresses unconditional and eternal support for a relationship or companionship that persists until the end of the world, or until the other person becomes very old with white hair, highlighting a promise to remain loyal and present no matter what happens over time