Śatapatha Brāhmaṇa ("of a hundred paths") 2.3.2.10

2.3.2.10

atha yatraitatpradīptataro bhavati | tarhi haiṣa bhavati varuṇaḥ sa yaḥ kāmayeta yathemā varuṇaḥ prajā gṛhṇanniva tvatsahaseva tvannighātamiva tvatsacata evamannamadyāmiti tarhi ha sa juhuyātprāpnoti haivaitadannādyaṃ ya evaṃ vidvāṃstarhi juhoti

And when it burns rather brightly, then indeed that (fire) is Varuna. And if any one desires to consume food,--even as Varuna seeks after these creatures, now, as it were, seizing on them, now with violence, now in striking them down,--let him offer then: and, assuredly, he who, knowing this, offers then, obtains that food.