Agnipurana 150.25

150.25

audgātraṃ sāmabhioś cakre brahmatvañcāpyatharvabhiḥ /
prathamaṃ vyāsaśiṣyastu pailo hy ṛgvedapāragaḥ //

the duty of the udgātṛ priest he made with the Sāmans, and the office of the brahman priest with the Atharvans. / First, Paila, a disciple of Vyāsa, was master of the Ṛgveda;