Shiva Purana
कुर्यात्त्रिषवणस्नानं भस्मस्नानमथापि वा ॥ पूजां वैशेषिकीं चैव मनसा वचसा गिरा ॥ ६८ ॥
He shall bathe thrice a day or he shall dust with the ashes instead. He shall perform special worship mentally, verbally and physically.
english translation
kuryAttriSavaNasnAnaM bhasmasnAnamathApi vA ॥ pUjAM vaizeSikIM caiva manasA vacasA girA ॥ 68 ॥
hk transliteration by Sanscript