Śatapatha Brāhmaṇa ("of a hundred paths") 1.1.1.17

1.1.1.17

tato devā etaṃ vajraṃ dadṛśuḥ | yadapo vajro vā āpo vajro hi vā āpastasmādyenaitā yanti nimnaṃ kurvanti yatropatiṣṭhante nirdahanti tata etaṃ vajramudayacaṃstasyābhaye 'nāṣṭre nivāte yajñamatanvata tatho evaisa etaṃ vajramudyacati tasyābhaye 'nāṣṭre nivāte yajñaṃ tanute tasmādapaḥ praṇayati

The gods then perceived this thunderbolt, to wit, the water: the water is a thunderbolt, for the water is indeed a thunderbolt; hence wherever it goes, it produces a hollow (or depression of ground); and whatever it comes near, it destroys (lit. it burns up). Thereupon they took up that thunderbolt, and in its safe and foeless shelter they spread (performed) the sacrifice. And thus he (the Adhvaryu priest) likewise takes up this thunderbolt, and in its safe and foeless shelter spreads the sacrifice. This is the reason why he brings forward water.