Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.9

2.5.2.9

ubhayatra payasye bhavataḥ | payaso vai prajāḥ sambhavanti payasaḥ sambhūtāstadyata eva sambhūtā yataḥ sambhavanti tata evaitadubhayato varuṇapāśātprajāḥ pramuñcatītaścordhvā itaścāvācīstasmādubhayatra payasye bhavataḥ

On both (fires) there is an oblation of curds. It is on milk that the creatures subsist and by means of milk that they were preserved: hence it is with that by which they were preserved and whereon they subsist, that he delivers them both ways from Varuna's noose,--on the one side (he delivers) the upright and on the other those looking to the ground. This is why there is an oblation of curds on both (fires).