Matsya Purana — The Attendant Hosts of the Sun and Moon: Monthly Gaṇas
आपूर्यते परो भागः सोमस्य तु अहःक्रमात् ततः पीतक्षयं सोमं युपगद्व्यापयन् रविः //
āpūryate paro bhāgaḥ somasya tu ahaḥkramāt tataḥ pītakṣayaṃ somaṃ yupagadvyāpayan raviḥ //
Day by day, the further portion of Soma (the Moon) becomes filled in due order. Thereafter, when Soma has been diminished by being ‘drunk’ by the gods, Ravi (the Sun), moving on his course, causes Soma to wane to depletion.
This verse is not about Pralaya; it explains a cyclical cosmic process—how the Moon waxes and wanes—showing orderly celestial regulation rather than dissolution.
By grounding time in lunar change, it supports dharma based on calendrical observance—tithis, fasting days, śrāddha timing, and ritual scheduling—key responsibilities for householders and rulers who maintain public rites.
The ritual takeaway is calendrical: lunar waxing/waning underlies tithi-based rites (vratas, darśa-pūrṇamāsa, śrāddha). No direct Vāstu/temple-measurement rule is stated in this verse.