Matsya Purana — Soma
इत्येष पर्वसंधीनां कालो वै द्विलवः स्मृतः पर्वणां तुल्यकालस्तु तुल्याहुतिवषट्क्रियाः //
ityeṣa parvasaṃdhīnāṃ kālo vai dvilavaḥ smṛtaḥ parvaṇāṃ tulyakālastu tulyāhutivaṣaṭkriyāḥ //
Thus, the time-span of the junctions (sandhi) between the ritual parvas is traditionally understood to be two lavas; and when the parvas have equal duration, the oblations (āhuti) and the vaṣaṭ-acclamations in the rite are to be performed in equal measure as well.
This verse is not about pralaya; it is a technical rule on ritual timekeeping, defining the duration of parva-junctions (sandhis) as two lavas.
For a king or householder who sponsors yajñas, it stresses disciplined scheduling: offerings (āhuti) and vaṣaṭ recitations should be proportionate and evenly performed when ritual segments are of equal duration.
The significance is ritual: it standardizes the ‘sandhi’ time (two lavas) and prescribes equalized homa actions—equal oblations and vaṣaṭ-acts—when parvas are equal, supporting precise liturgical procedure.