Shiva Purana
ध्यात्वा शिवं च तं साम्बं जपन्पञ्चाक्षरम्मनुम् ॥ समभ्यर्च्य चिरं कालं चचार परमन्तपः ॥ १७ ॥
He meditated on Śiva along with Pārvatī repeating the five-syllabled mantra. Worshipping thus he performed great penance for a long time.
english translation
dhyAtvA zivaM ca taM sAmbaM japanpaJcAkSarammanum ॥ samabhyarcya ciraM kAlaM cacAra paramantapaH ॥ 17 ॥
hk transliteration by Sanscript