山盟海誓你依在天荒地久你依爱
[shān méng hăi shì nĭ yī zài tiān huāng dì jiŭ nĭ yī ài]
'Vowing by mountains and seas you are still there, and till the world's end you're loved' refers to making oaths as eternal as nature. It promises loyalty over an immeasurably long span of time and implies undying love despite great odds.