Matsya Purana — The Syamantaka Jewel Episode and the Vrishni–Sainya Genealogies
ततः प्रविश्य स बिलं प्रसेनो ह्य् ऋक्षमैक्षत ऋक्षः प्रसेनं च तथा ऋक्षं चैव प्रसेनजित् //
tataḥ praviśya sa bilaṃ praseno hy ṛkṣamaikṣata ṛkṣaḥ prasenaṃ ca tathā ṛkṣaṃ caiva prasenajit //
Then, entering that cave, Prasena indeed saw a bear; and the bear saw Prasena. Likewise, Prasenajit also saw both Prasena and the bear.
Nothing directly—this verse is a narrative scene describing a cave encounter, not cosmology or pralaya doctrine.
Indirectly, it frames a royal-family crisis (Prasenajit and Prasena) where vigilance, investigation, and responsibility for one’s dependents are implied—common ethical motifs in Purāṇic kingship narratives.
No explicit vāstu or ritual rule is stated; the only setting detail is the “bila” (cave), serving as a narrative locus rather than architectural instruction.