我许你一生天荒地老我还你一世地久天长
[wŏ xŭ nĭ yī shēng tiān huāng dì lăo wŏ hái nĭ yī shì dì jiŭ tiān zhăng]
It conveys a romantic and heartfelt promise between two lovers. It translates to making a vow together lasting from young till old, through every twist of fate, embodying eternal love and commitment.