Matsya Purana — Vrata-Ṣaṣṭhī: The Sixty Sacred Vows
सप्तम्यां नक्तभुग्दद्यात् समान्ते गां पयस्विनीम् सूर्यलोकमवाप्नोति भानुव्रतमिदं स्मृतम् //
saptamyāṃ naktabhugdadyāt samānte gāṃ payasvinīm sūryalokamavāpnoti bhānuvratamidaṃ smṛtam //
On Saptamī (the seventh lunar day), one should eat only at night and, at the completion of the observance, gift a milk-yielding cow. By this one attains the world of the Sun; this is remembered as the Bhānu-vrata (vow of the Sun).
This verse is not about pralaya; it teaches vrata-dharma—how a Sun-focused vow (Bhānu-vrata) yields a specific posthumous result, namely attainment of Sūryaloka.
It prescribes a disciplined observance (night-only eating on Saptamī) and a concluding act of generosity (donating a milk-giving cow), reflecting the householder duty of combining self-restraint with dāna for merit.
The ritual significance is vrata procedure and phala: Saptamī observance with naktabhojana and go-dāna as the concluding gift, oriented to Sūrya-upāsanā rather than Vāstu or temple construction.