Skandapurana 1.3.5.31

1.3.5.31

oṃkāraṃ narmadāyāṃ ca mahākālaṃ tathaiva ca..
kāśyāṃ viśveśvaraṃ devaṃ prayāge laliteśvaram.. 7.31 ..

Oṃkāra on the Narmadā, and likewise Mahākāla; / The god Viśveśvara in Kāśī, and Laliteśvara in Prayāga;