Matsyapurana 95.6

95.6

mārgaśīrṣatrayodaśyāṃ sitāyāmekabhojanaḥ
prārthayeddevadeveśaṃ tvāmahaṃ śaraṇaṃ gataḥ //

In the month of Mârgaśirâ, on the thirteenth day of the bright fortnight, the devotee should take his meals once and pray to Śiva with this Saṅkalpa mantra, “O Lord of all the Deities! I take refuge in Thee. To-morrow, the Chaturdaśî day, I shall observe a complete fast, without eating anything, and worship Śiva. I shall also give away a bull, made of gold, and then take my meals the next day.”—6-7.