Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.4.1

2.6.4.1

tadyadāhuḥ | sākamedhairvai devā vṛtramaghnaṃstairveva vyajayanta yeyameṣāṃ vijitistāmiti sarvairha tveva devāścāturmāsyairvṛtramaghnantsarvairveva vyayanta yeyameṣāṃ vijitistām

Now when it is said, that the gods, by means of the Sâkamedha -offerings, slew Vritra and gained that supreme authority which they now wield,--it is rather by means of all the Seasonal sacrifices that the gods slew Vritra; it is by all of them that they gained that supreme authority which they now wield.