Matsya Purana — Sādhāraṇa Śrāddha: General Ancestral Rite
ततस्तु वैश्वदेवान्ते सभृत्यसुतबान्धवः भुञ्जीतातिथिसंयुक्तः सर्वं पितृनिषेवितम् //
tatastu vaiśvadevānte sabhṛtyasutabāndhavaḥ bhuñjītātithisaṃyuktaḥ sarvaṃ pitṛniṣevitam //
Then, at the conclusion of the Vaiśvadeva rite, together with his servants, sons, and kinsmen, he should take his meal in the company of a guest—partaking only of what has first been duly offered in service to the Pitṛs (ancestors).
This verse is not about Pralaya; it teaches daily dharma—specifically the proper sequence of eating only after completing Vaiśvadeva and honoring the Pitṛs and guests.
It states a core gṛhastha rule: after the Vaiśvadeva rite, one should eat with dependents and relatives while honoring an atithi, and only consume food that has first been ritually allocated to the ancestors—linking personal sustenance to social responsibility and sacred obligation.
The significance is ritual (not architectural): it specifies the timing and precedence—Vaiśvadeva completion, then guest-inclusion, and consumption of food only after Pitṛ-related offering/attendance.