Śatapatha Brāhmaṇa ("of a hundred paths") 4.5.6.5

4.5.6.5

tānvai na sarvamivāvakāśayet | yo nveva jñātastamavakāśayedyo vāsya priyaḥ syādyo vānūcāno 'nūktenainānprāpnuyātsa āśvinaṃ grahaṃ gṛhītvā kṛtsnaṃ yajñaṃ janayati taṃ kṛtsnaṃ yajñaṃ janayitvā tamātmandhatte tamātmankurute

He must not let every one eye them, but only him who is well known, or one who is his friend, or one who, being learned in sacred lore, may acquire these (texts) through study. Having drawn the Âsvina cup, he (thus) produces the whole sacrifice; and having produced the whole sacrifice, he deposits it in his own self, and makes it his own.