Śatapatha Brāhmaṇa ("of a hundred paths") 1.6.2.4

1.6.2.4

te hocuḥ | aśvibhyāṃ tiṣṭha sarasvatyai tiṣṭhendrāya tiṣṭheti sa sasarpaivāgnaye tiṣṭheti tatastasthāvagnaye vāasthāditi tamagnāveva parigṛhya sarvahutamajuhavurāhutirhidevānāṃ tata ebhyo yajñaḥ prārocata tamasṛjanta tamatanvata so 'yam paro 'varaṃ yajño 'nūcyate pitaiva putrāya brahmacāriṇe

They said, 'Stand still for the Asvins! stand still for Sarasvatî! stand still for Indra!' still it crept on;--'Stand still for Agni!' at this it stopped. Having then enveloped it in fire (Agni), knowing, as they did, that it had stopped for Agni, they Offered it up entirely, for it was an oblation to the gods. Then the sacrifice pleased them; they produced it, they spread it. And this same sacrifice is taught by the former to the later; the father (teaches it) to his son when he is a student (brahmakârin).