契阔死生

It's extracted from classical Chinese poetry with the meaning of enduring all vicissitudes of life together, which also involves being apart due to certain circumstances yet remaining true-hearted to each other in life and death. It often describes a deeply cherished relationship between friends, lovers, or spouses who go through hardships or distance, even until death, but maintain loyalty and sincerity towards each other. So it signifies loyalty under trying conditions, especially within close relationships.