Markandeyapurana 48.31

48.31

gāyatrīñca ṛcañcaiva trivṛt somaṃ rathantaram /
agniṣṭomañca yajñānāṃ nirmame prathamānmukhāt //

And for the sacrifices he fashioned from his front mouth the gāyatrī, and the tṛca strophe, the tri-vṛt hymn of praise,[20] the rathantara sāmans, and the agni-ṣṭoma verses. And he created from his right mouth the yajur hymns, the tri-ṣṭubh metre, sacred hymns,[21] and the fifteen hymns of praise,[22] and the bṛhat-sāman and the uktha verses.[23] He fashioned from his hindmost mouth the sāman hymns, the metre jagatī, and the fifteen hymns of praise,[24] the vairūpa sāman, and the atirātra verse.[25] He created from his left mouth the twenty-first Atharva hymn, and the aptor-yāman sacrificial verse,[25] the anū-ṣṭubh metre and the virāj metre.