Matsya Purana — Nārāyaṇa as Haṃsa in the Cosmic Ocean: Vedic Yajña-Puruṣa and Mārkaṇḍeya’s Vi...
अहं चैव सरिद्दिव्या क्षीरोदश्च महार्णवः यत्तत्सत्यं च परमम् अहमेकः प्रजापतिः //
ahaṃ caiva sariddivyā kṣīrodaśca mahārṇavaḥ yattatsatyaṃ ca paramam ahamekaḥ prajāpatiḥ //
I alone am that divine river; I am the Ocean of Milk and the great cosmic sea. Whatever is the Supreme and the Real—of that too I am the one source, the single Lord of progeny (Prajāpati).
It presents the Supreme as identical with the great waters and cosmic supports (river, Milk Ocean, cosmic sea), implying that in pralaya and creation alike, all rests in the One source.
By asserting a single supreme ground of truth and order, it underwrites dharma: a king or householder should rule and live aligned with satya (truth) and the higher principle rather than mere personal gain.
No direct Vāstu or iconographic rule is stated; indirectly, it supports ritual cosmology where waters (rivers/oceans) symbolize the all-containing divine reality invoked in purification and consecration rites.