Shiva Purana
तदतीतं च नैर्गुण्यादध्वनोस्य विशोधकम् ॥ द्वयोः प्रमापको नादो नदांतश्च मदात्मकः ॥ ४० ॥
The past is also the purifier of the path of non-virtue. The sound measuring both is the sound and the end of the sound is the ego.
english translation
tadatItaM ca nairguNyAdadhvanosya vizodhakam ॥ dvayoH pramApako nAdo nadAMtazca madAtmakaH ॥ 40 ॥
hk transliteration by Sanscript