Śatapatha Brāhmaṇa ("of a hundred paths") 11.2.4.10

11.2.4.10

tadāhuḥ āgūrtī vā eṣa bhavati yo darśapūrṇamāsābhyāṃ yajate paurṇamesena hīṣṭvā vedāmāvāsyena yakṣya ityāmāvāsyeneṣṭvā veda punaḥ paurṇamāsena yakṣya iti sa āgūrtyevāmuṃ lokameti yadāmuṃ lokameti kathamanāgūrtī bhavatīti sa yadevaitā ubhayatrāghārāvāghārayati tadevāsya darśapūrṇamāsau saṃtiṣṭhete sa saṃsthitayoreva darśapūrṇamāsayorathāmuṃ lokameti tathānāgūrtī bhavati

As to this they say, 'Surely, he who performs the Full and New-moon offerings becomes a (mere) utterer of the Âgur; for, when he has performed the Full-moon offering, he knows that he will perform the New-moon offering; and when he has performed the New-moon offering, he knows that he will again perform the Full-moon offering; thus when he goes to the other world he goes thither as an utterer of the Âgur: how, then, does he become one who has not (merely) uttered the Âgur?' Well, when, on both occasions, he makes those two libations of ghee (to Mind and Speech), then his Full and New-moon offerings become complete; and he goes to the other world after his Full and New-moon offerings are completed, and thus becomes one who has not (merely) uttered the Âgur.