Shatapatha Brahmana 5.2.5.13

5.2.5.13

atha śvo bhūte | vaiśvānaraṃ dvādaśakapālam puroḍāśaṃ nirvapati vāruṇa yavamayaṃ caruṃ tābhyāmanūcīnāhaṃ veṣṭibhyāṃ yajate samānabarhirbhyāṃ vā

And on the following day he prepares a cake-on twelve potsherds for (Agni) Vaisvânara, and a barley pap for Varuna. These two offerings he performs either on days following one another, or so as to use the same barhis.