Matsya Purana — The Procedure and Merit of the Śubha-Saptamī Vrata
पुण्येन चाश्वयुजे मासि कृतस्नानजपः शुचिः वाचयित्वा ततो विप्रान् आरभेच्छुभसप्तमीम् //
puṇyena cāśvayuje māsi kṛtasnānajapaḥ śuciḥ vācayitvā tato viprān ārabhecchubhasaptamīm //
In the holy month of Āśvayuja, having bathed and performed japa, remaining pure, one should then have brāhmaṇas recite the sacred texts and thereafter begin the auspicious Saptamī observance.
This verse does not address pralaya; it focuses on vrata-dharma—purificatory bathing, japa, and beginning an auspicious Saptamī observance in Āśvayuja.
It prescribes a householder-style dharmic routine: maintain purity, perform snāna and japa, honor learned brāhmaṇas through recitation, and then undertake the vow—model conduct applicable to rulers as well as householders.
The significance is ritual (not architectural): the rite is to be initiated after purification and after arranging brāhmaṇa-led recitation, indicating that correct sequencing and śauca (purity) are essential to the Saptamī vrata.