Śatapatha Brāhmaṇa ("of a hundred paths") 2.3.1.30

2.3.1.30

sa juhoti | agnirjyotirjyotiragniḥ svāhetyatha prātaḥ sūryo jyotirjyotiḥ sūryaḥ svāheti tatsatyenaiva hūyate yadā hyevasūryo 'stametyathāgnirjyotiryadā sūrya udetyatha sūryo jyotiryadvai satyena hūyate taddevān gacati

[In the evening] he offers (the first libation), with the text (Vâg. S. III, 9, 10), 'Agni is the light, the light is Agni, Svâhâ!' and in the morning with, 'Sûrya (the sun) is the light, the light is Sûrya, Svâhâ!' Thus offering is made with the truth; for, truly, when the sun goes down, then Agni (fire) is the light, and when the sun rises, then Sûrya is the light; and whatever is offered with the truth, that, indeed, goes to the gods.