Śatapatha Brāhmaṇa ("of a hundred paths") 2.3.1.38

2.3.1.38

atha prātaḥ | sajūrdevena savitreti tatsavitṛmatprasavāya sajūruṣasendravatyetyahneti vā tadahnāṃ voṣasāṃ vā mithunaṃ karoti sendra karotīndro hi yajñasya devatā juṣāṇaḥ sūryo vetu svāheti tatsūryāya pratyakṣaṃ juhoti tasmādevameva juhuyāt

And in the morning with, 'Along with the divine Savitri--,' whereby it becomes possessed of Savitri for his impulsion; '--along with the Dawn, wedded to Indra,' or 'along with the Day....--,' whereby he effects a union either with the day or the dawn, and makes it (the sacrifice) possessed of Indra; for Indra is the deity of sacrifice; '--may Sûrya graciously accept! Svâhâ!' whereby he offers to Sûrya directly: hence he may offer in this way.