Matsya Purana — Vrata-Ṣaṣṭhī: The Sixty Sacred Vows
कार्त्तिक्यां च वृषोत्सर्गं कृत्वा नक्तं समाचरेत् शैवं पदमवाप्नोति वार्षव्रतमिदं स्मृतम् //
kārttikyāṃ ca vṛṣotsargaṃ kṛtvā naktaṃ samācaret śaivaṃ padamavāpnoti vārṣavratamidaṃ smṛtam //
Having performed the vṛṣotsarga rite (the ritual gift/release of a bull) in the month of Kārttika, one should observe the vow of eating only at night; by this, one attains the Śaiva state, the abode of Śiva. This is remembered as the vārṣa-vrata (“annual vow”).
This verse does not address pralaya or cosmology; it focuses on vrata-dharma—ritual observance in Kārttika and its salvific fruit.
It presents a practical householder vow: perform vṛṣotsarga (a meritorious donation/rite involving a bull) and keep the nakta discipline (eating only at night), framing ethical giving and self-restraint as duties that lead to spiritual attainment.
The ritual significance is vṛṣotsarga in Kārttika combined with the nakta vow; the text states its fruit as reaching the Śaiva abode, marking it as an “annual vow” (vārṣa-vrata).