Shiva Purana
रुद्रा क्षेण जपन्मन्त्रं पुण्यं कोटिगुणं भवेत् । दशकोटिगुणं पुण्यं धारणाल्लभते नरः ५८ ।
A mantra repeated with Rudrākṣa is a crore times more efficacious. A man wearing Rudrākṣa derives a hundred million times more merit.
english translation
rudrA kSeNa japanmantraM puNyaM koTiguNaM bhavet । dazakoTiguNaM puNyaM dhAraNAllabhate naraH 58 ।
hk transliteration by Sanscript