Matsya Purana — Vrata-Ṣaṣṭhī: The Sixty Sacred Vows
उपवासं परित्यज्य समान्ते गोप्रदो भवेत् यक्षाधिपत्यमाप्नोति सुखव्रतमिदं स्मृतम् //
upavāsaṃ parityajya samānte goprado bhavet yakṣādhipatyamāpnoti sukhavratamidaṃ smṛtam //
After completing the fast, one should conclude by gifting a cow. By this observance, one attains lordship among the Yakṣas; this is remembered as the Sukha-vrata (the vow that brings ease and well-being).
This verse does not address pralaya or cosmogony; it is a phala-śruti passage describing the spiritual result of completing a vow with charity.
It frames dharma as disciplined restraint (fasting) completed by dāna (cow-gift). For householders and rulers alike, the verse emphasizes that religious observances should culminate in public-spirited generosity, not mere self-mortification.
The ritual takeaway is procedural: a vrata is concluded (samānte) by a prescribed donation—go-dāna—highlighting correct completion rites rather than any Vāstu or temple-building rule.