Matsya Purana — Soma
एवमाप्यायते सोमः क्षयिते च पुनः पुनः समृद्धिरेवं सोमस्य पक्षयोः शुक्लकृष्णयोः //
evamāpyāyate somaḥ kṣayite ca punaḥ punaḥ samṛddhirevaṃ somasya pakṣayoḥ śuklakṛṣṇayoḥ //
Thus Soma (the Moon) becomes replenished again and again after having waned; in this very way does the Moon’s increase and decrease occur through its two fortnights—the bright (waxing) and the dark (waning).
It does not describe Pralaya directly; it highlights the recurring cosmic rhythm of increase and decrease—an example of orderly cycles that continue through time.
By grounding ritual and civic life in the lunar calendar: household rites, fasting days, and royal ceremonies are traditionally scheduled by śukla/kr̥ṣṇa pakṣa, so understanding the Moon’s waxing/waning supports dharmic observance.
Ritually, it supports pakṣa-based timing (tithis and fortnight observances) used for temple worship schedules, vratas, and consecration planning, even though no specific Vastu rule is stated in this verse.