相濡以沫的誓言长相厮守的诺言
[xiāng rú yĭ mò de shì yán zhăng xiāng sī shŏu de nuò yán]
This phrase means a vow between two people who pledge to stay together for a long time and live in harmony. In traditional culture, it refers to the deep bond of love between couples in adversity, indicating their intention to remain loyal to each other despite hardships, much like fish moistening each other's mouths during drought.