Matsya Purana — Soma
कलाः क्षीयन्ति कृष्णास्ताः शुक्ला ह्याप्याययन्ति च एवं सा सूर्यवीर्येण चन्द्रस्याप्यायिता तनुः //
kalāḥ kṣīyanti kṛṣṇāstāḥ śuklā hyāpyāyayanti ca evaṃ sā sūryavīryeṇa candrasyāpyāyitā tanuḥ //
During the dark fortnight (kṛṣṇa-pakṣa) those kalās diminish, while in the bright fortnight (śukla-pakṣa) they increase. Thus the Moon’s body is replenished and made to wax by the Sun’s potency (vīrya).
It does not describe Pralaya directly; it explains cyclical cosmic regulation—how lunar waxing and waning occur—reflecting orderly time (kāla) rather than dissolution.
By grounding ritual and civic life in lunar time: householders and kings schedule vratas, śrāddhas, festivals, and administrative observances by Shukla/Krishna Paksha and tithis, which depend on the Moon’s waxing and waning described here.
Ritually, it supports lunar-calendar timing for temple rites and fasts (e.g., pūrṇimā/amāvāsyā observances). Architecturally, it has indirect relevance through calendrical selection of auspicious days (muhūrta) for construction and consecration.