Pranatoshini 2.19.1

Prāṇatoṣiṇī 2.19.1

mantrāṇāṃ varṇamayatvāt varṇaprakaraṇānantaraṃ mantraprakaraṇasyaucityāt
mantraprakaraṇamucyate viśvasāratantre tṛtīyapaṭale ||