Matsya Purana — Inquiry into Yayāti’s Story and the Kacha–Devayānī Episode
व्रतं च व्रतकालं च यथोक्तं प्रत्यगृह्णत आराधयन्नुपाध्यायं देवयानीं च भारत //
vrataṃ ca vratakālaṃ ca yathoktaṃ pratyagṛhṇata ārādhayannupādhyāyaṃ devayānīṃ ca bhārata //
He duly accepted the vow and its prescribed duration exactly as instructed, worshipping and serving his preceptor; and he attended upon Devayānī as well, O Bhārata.
This verse does not discuss Pralaya; it highlights dharmic discipline—undertaking a prescribed vow and honoring the teacher—within a genealogical/itihāsa narrative.
It models core duties praised in the Matsya Purāṇa—observing vratas with exactness (yathoktam) and practicing guru-sevā (service to the preceptor), virtues expected of householders and rulers alike for self-control and legitimacy.
The ritual significance is the correct undertaking of a vrata along with its specified duration (vrata-kāla), emphasizing procedural accuracy in religious observances rather than Vāstu or temple-construction rules.