Matsya Purana — Characteristics of Dvāpara and Kali Yugas
एको वेदश्चतुष्पादः संहृत्य तु पुनः पुनः संक्षेपादायुषश्चैव व्यस्यते द्वापरेष्विह //
eko vedaścatuṣpādaḥ saṃhṛtya tu punaḥ punaḥ saṃkṣepādāyuṣaścaiva vyasyate dvāpareṣviha //
The one Veda, four-footed (complete in four quarters), is repeatedly gathered up; and then, for the sake of brevity and in view of the shortening of human lifespan, it is here arranged and divided in the Dvāpara ages.
Directly, it addresses not Pralaya but yuga-wise decline: as lifespan shortens, the Veda is repeatedly recompiled and systematized so it remains accessible after cosmic and historical transitions.
It implies that dharma must be practiced according to one’s era and capacity: rulers and householders should rely on the organized Vedic teaching of their time (as arranged in Dvāpara) rather than claim an unattainable, earlier-yuga standard.
No Vāstu rule is stated here; the ritual takeaway is that sacrifices and rites depend on Vedic transmission, and the Veda’s division/arrangement safeguards correct ritual performance despite diminishing human longevity.