Shiva Purana
नात्यंतं प्रतिपद्यंते शिवयाथात्म्यवेदनात् ॥ आत्मस्थं यः शिवं त्यक्त्वा बहिरभ्यर्चयेन्नरः ॥ ५६ ॥
They do not attain to the extreme because of the pain of the reality of Lord Śiva. Anyone who worships Lord Śiva outside the self should worship him externally.
english translation
nAtyaMtaM pratipadyaMte zivayAthAtmyavedanAt ॥ AtmasthaM yaH zivaM tyaktvA bahirabhyarcayennaraH ॥ 56 ॥
hk transliteration by Sanscript