Matsya Purana — Yuga Durations
ब्राह्मण्यभावस्य ततस् तथौत्सुक्यं विशीर्यते व्रतोपवासास्त्यज्यन्ते द्वापरे युगपर्यये //
brāhmaṇyabhāvasya tatas tathautsukyaṃ viśīryate vratopavāsāstyajyante dvāpare yugaparyaye //
Then the very disposition of brahminical virtue declines, and with it the zeal for sacred duties withers away; at the close of the Dvāpara Yuga, vows and fasts are abandoned.
This verse is not about cosmic pralaya; it describes a moral-spiritual decline at the yuga transition, where religious discipline (vrata, upavāsa) and brahminical virtue weaken.
It functions as a warning: as public zeal for dharma fades near the end of Dvāpara, rulers and householders must consciously preserve vows, fasting, and ethical discipline rather than following the general decline.
The ritual point is explicit: traditional vratas and upavāsas are abandoned in the yuga’s downturn, highlighting the Matsya Purana’s concern for maintaining Vedic-Puranic observances even when social practice deteriorates.