Śatapatha Brāhmaṇa ("of a hundred paths") 14.2.1.13

14.2.1.13

indrāya pinvasveti indro vai yajñasya devatā sā yaiva yajñasya devatā tayaivaitadaśvinau yajñasya śiraḥ pratyadhattāṃ tāvevaitatprīṇāti tasmādāhendrāya pinvasveti

'Flow for Indra!'--for Indra is the deity of the sacrifice, and it was indeed by him who is the deity of the sacrifice that the Asvins then restored the head of the sacrifice: it is them he thus pleases, and therefore he says, 'Flow for Indra!'