我们山盟海誓海枯石烂我们天荒地老天长地久
[wŏ men shān méng hăi shì hăi kū shí làn wŏ men tiān huāng dì lăo tiān zhăng dì jiŭ]
It describes 'we made oaths by mountains and oceans, and we would love each other forever.' Emphasizing a very passionate and eternal vow of love between individuals.