In the Ramcharitmanas, Tulsidas’s retelling of the Ramayana, King Dasharatha has promised Queen Kaikeyi two boons. She asks that her son Bharat be crowned and that Rama be sent into exile for fourteen years. Dasharatha is broken by grief, but he keeps his word.
The poem explains it in one line: Raghukul reet sada chali aayi, pran jaye par bachan na jaai. It has always been the rule in the house of Raghu. Life may go, but a promise may not.