Shatapatha Brahmana 5.1.5.15

5.1.5.15

tadyathaivādo bṛhaspatiḥ | savitāram prasavāyopādhāvatsavitā vai devānām prasavitedam me prasuva tvatprasūta idamujjayānīti tadasmai savitā prasavitā prāsuvatatsavitṛprasūta udajayadevamevaiṣa etatsavitārameva prasavāyopadhāvati savitā vai devānām prasavitedam me prasuva tvatprasūta idamujjayānīti tadasmai savitā prasavitā prasauti tatsavitṛprasūta ujjayati

And whichever (horse) he yokes with a formula, up to that the Sacrificer now steps, with (Vâg. S. IX, 13), 'At the impulse of the divine Savitri, of true impulsion, may I win the race of the race-winning Brihaspati!'