Skandapurana 6.3.178.26

6.3.178.26

tasminparvaṇi deveśi śaṅkhaṃ saṃspṛśya mānavaḥ .
snānamācarate toye miśre gāṅgeyanārmade .. 178.26 ..

On that holy occasion, O goddess of the gods, a person having touched the conch / performs a ritual ablution in the mingled water of Gaṅgā and Narmadā;