Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 85.64

85.64

śrīmārkaṇḍeya uvāca:
somanāthaprabhāvo 'yaṃ śṛṇuṣvaikamanā vidhim /
aṣṭamyāṃ vā caturdaśyāṃ sarvakālaṃ raverdine //

The venerable Mārkaṇḍeya said: / This is the power of Somanātha. Listen with single-minded attention to the rite / on the eighth or the fourteenth [day], and at all times on the day of Ravi;