Skandapurana 6.3.43.27

6.3.43.27

tathāniṣṭatarāṇāṃ hi rudrasya vacanaṃ yathā .
narmadā saritāṃ śreṣṭhā rudradehādviniḥsṛtā .. 43.27 ..

So too, for those who are most undesirable, according to Rudra's word:
the Narmadā, the best of rivers, came forth from Rudra's body.