Agnipurana 150.24

150.24

ekaścāsīd yajurvedastaṃ caturdhā vyakalpayat /
ādhvaryavaṃ yajurbhistu ṛgbhirhotraṃ tathā muniḥ //

And the Yajurveda was one; he arranged it into four parts. / The sage [constituted] the duty of the adhvaryu priest with the Yajuses, and that of the hotṛ priest with the Ṛcs;