Shiva Purana
अतिवर्णाश्रमी नित्यं शिवोहं भावनात्परात् । शिवयोगी च नियतमीशानेनापि धारयेत् ३७ ।
A Śivayogin being outside the pale of Varṇa and Āśrama rites because of his conception “I am Śiva” shall wear ashes with the Īśāna mantra.
english translation
ativarNAzramI nityaM zivohaM bhAvanAtparAt । zivayogI ca niyatamIzAnenApi dhArayet 37 ।
hk transliteration by Sanscript