Shiva Purana
इत्युक्त्वा दंडवद्भूमौ प्रणिपत्य शिवं शिवाम् ॥ जपेत्पञ्चाक्षरीं विद्यामष्टोत्तरशतावराम् ॥ १७९ ॥
After saying this he shall prostrate before Śiva and Śivā and perform the Japa of the five-syllabled mantra not less than hundred and eight times.
english translation
ityuktvA daMDavadbhUmau praNipatya zivaM zivAm ॥ japetpaJcAkSarIM vidyAmaSTottarazatAvarAm ॥ 179 ॥
hk transliteration by Sanscript