Matsya Purana — The Attendant Hosts of the Sun and Moon: Monthly Gaṇas
इत्येवं सूर्यवीर्येण चन्द्रस्याप्यायते तनुः पौर्णमास्यां प्रदृश्येत शुक्लः सम्पूर्णमण्डलः //
ityevaṃ sūryavīryeṇa candrasyāpyāyate tanuḥ paurṇamāsyāṃ pradṛśyeta śuklaḥ sampūrṇamaṇḍalaḥ //
Thus, by the Sun’s vital potency, the Moon’s body is nourished and increases; and on the full-moon night it is seen as bright—its orb complete and entire.
It does not describe Pralaya directly; it explains a cosmological mechanism—how the Moon waxes through the Sun’s potency—supporting the Purāṇic model of an ordered universe governed by celestial principles.
By grounding the lunar cycle in cosmic order, it supports dharmic timekeeping: householders and rulers schedule vratas, dāna, and public rites by tithi—especially Paurṇimā—so governance and domestic ritual align with auspicious calendrical rhythms.
The ritual significance is calendrical: Paurṇimā is highlighted as the moment of the Moon’s complete brilliance, a key timing marker for full-moon worship, fasts, offerings, and temple rites that follow lunar tithis.