Matsya Purana — Code of Conduct and Vow-Procedure for Courtesans
एवमादित्यवारेण सर्वमेतत्समाचरेत् तण्डुलप्रस्थदानं च यावन्मासास्त्रयोदश //
evamādityavāreṇa sarvametatsamācaret taṇḍulaprasthadānaṃ ca yāvanmāsāstrayodaśa //
Thus, on Sundays one should duly perform all these observances; and one should also donate a prastha-measure of rice, continuing this for thirteen months.
This verse does not discuss pralaya; it focuses on dharma in the form of Sunday observance and sustained charity (rice donation) over a fixed period.
It frames a practical householder/royal duty: regular vrata-performance and dāna (measured rice-gift) carried out with consistency for thirteen months—an ethic of disciplined giving and ritual responsibility.
The significance is ritual (vrata-vidhi), specifying the weekday (Sunday), the act (perform all prescribed rites), and the concrete dāna item/quantity (one prastha of rice) maintained for thirteen months.