Śatapatha Brāhmaṇa ("of a hundred paths") 4.3.5.2

4.3.5.2

te hādityā ūcuḥ | yathedamamiśraṃ vasūnāṃ prātaḥsavanamamiśraṃ rudrāṇām mādhyandinaṃ savanamevaṃ na imam purā miśrādgrahaṃ juhutheti tatheti devā abruvaṃste saṃsthita eva mādhyandine savane purā tṛtīyasavanādetamajuhavuḥ sa eṣo 'pyetarhi tathaiva graho hūyate saṃsthita eva mādhyandine savane purā tṛtīyasavanāt

The Âdityas then said, 'As that morning pressing belongs exclusively to the Vasus, and that midday pressing exclusively to the Rudras, so offer ye now to us a libation before the common (pressing).' The gods said, 'So be it!' After the completion of the midday pressing, they offered that (libation) previous to the third pressing. And in like manner is that libation offered to this day after the completion of the midday pressing and previous to the third pressing.