Matsya Purana — Origin of Soma
तद्दिशो जगृहुर्धाम स्त्रीरूपेण सुतेच्छया गर्भो भूत्वोदरे तासाम् आस्थितो ऽब्दशतत्रयम् //
taddiśo jagṛhurdhāma strīrūpeṇa sutecchayā garbho bhūtvodare tāsām āsthito 'bdaśatatrayam //
Then, from those regions, a divine being assumed a woman’s form out of the desire for offspring; becoming an embryo, it remained established in their womb for three hundred years.
This verse does not directly describe Pralaya; it highlights a mythic conception motif where a divine presence enters the womb and remains for an extraordinary duration, typical of Purāṇic cosmological time scales.
Indirectly, it emphasizes the Purāṇic ideal of lineage and progeny (suta-icchā). In the broader Matsya Purana, continuity of dharma through righteous offspring and protected succession is a recurring ethical theme for rulers and householders.
No Vāstu or temple-architecture rule is stated here; the verse is narrative and focuses on divine embodiment and gestation rather than ritual procedure or building prescriptions.