Agniveshyagrihyasutra 1.1.4.41

1.1.4.41

trivṛtā annena brāhmaṇān pariviṣya puṇyāhaṃ svastyayanamṛddhiṃ vācayitvā tryahavrataṃ caratyakṣāralavaṇamaśamīdhānyaṃ bhuñjānaḥ adhaśśāyī amṛṇmayapāyī aśūdrocchiṣṭamadhumāṃsāśī adivāsvāpī ubhau kālau bhikṣācaryamudakumbhamityāharannaharahaḥ kāṣṭhakalām \

Having served Brahmins with threefold food and having made them pronounce the blessing for an auspicious day, safety, and prosperity, he observes the three-day vow: eating food without pungent condiments or salt and without pulse grain, sleeping on the ground, not drinking from an earthen vessel, not eating the leftovers of a Śūdra, honey, or meat, not sleeping by day, going out to beg alms at both twilight times, bringing a water-pot, [and] bringing every day a bundle of firewood.