Matsya Purana — Nārāyaṇa as Haṃsa in the Cosmic Ocean: Vedic Yajña-Puruṣa and Mārkaṇḍeya’s Vi...
स्वपित्येकार्णवे चैव यदाश्चर्यमभूत्पुरा श्रूयतां तद्यथा विप्रा मार्कण्डेयकुतूहलम् //
svapityekārṇave caiva yadāścaryamabhūtpurā śrūyatāṃ tadyathā viprā mārkaṇḍeyakutūhalam //
And hear as well, O brahmins, what wondrous event once occurred in the single cosmic ocean (Ekārṇava) while (Nārāyaṇa) lay in yogic sleep—namely, the curious marvel experienced by Mārkaṇḍeya.
It introduces a pralaya setting: the universe reduced to the single cosmic ocean (Ekārṇava) while the supreme being rests in yogic sleep, framing the coming episode as a dissolution-era marvel.
Indirectly, it models the Purāṇic ethic of śravaṇa (attentive listening) to sacred history—an advised discipline for householders and rulers to gain discernment and steadiness amid impermanence.
None explicitly in this verse; it is a narrative preface in the pralaya cycle rather than a Vāstu or ritual prescription.