Matsya Purana — Soma
अर्धमासस्य पर्वाणि द्वितीयाप्रभृतीनि च अग्न्याधानक्रिया यस्मान् नीयन्ते पर्वसंधिषु //
ardhamāsasya parvāṇi dvitīyāprabhṛtīni ca agnyādhānakriyā yasmān nīyante parvasaṃdhiṣu //
The observance-days (parva) of the half-month—beginning from the second lunar day (dvitīyā)—are so called because the rites of establishing the sacred fires (agnyādhāna) are performed at the junctions (sandhi) of those parva-days.
This verse is not about Pralaya; it defines ritual time-structure (parva and sandhi) and links it to agnyādhāna, emphasizing orderly sacred timing rather than cosmological dissolution.
It supports gṛhastha-dharma: establishing and maintaining sacred fires is a core Vedic duty, and the verse specifies that such rites should be aligned with parva-junctions within the fortnightly lunar calendar.
Ritually, it highlights correct timing (parva-sandhi) for agnyādhāna—key for yajña continuity; while not Vāstu-focused, it underpins the broader discipline of properly instituted sacred-fire rites.