Skandapurana 5.211.41

5.211.41

yena niryāti te kuṣṭho bhāskarasyodayaṃ prati ..
tacchrutvā'haṃ ca tatprāptaḥ saptamyāṃ sūryasaṃyuji ..
tataśca kṛtavānsnānaṃ nirjhare tatra śāṃbhave ..41..

whereby your leprosy will depart at the rising of the Sun.’ / Having heard that, I also reached that [place] on a seventh lunar day connected with a Sunday, / and then performed ritual ablution there in the cascade sacred to Śambhu.