Shiva Purana
अथ पंचाक्षरं नित्यं जपेदयुतमादरात् । संध्ययोश्च सहस्रं वा ज्ञेयं शिवपदप्रदम् ३९ ।
Or the devotee can with due reverence repeat the five-syllabled mantra ten thousand times every day or a thousand times at dawn and at dusk. It accords the region of Śiva.
english translation
atha paMcAkSaraM nityaM japedayutamAdarAt । saMdhyayozca sahasraM vA jJeyaM zivapadapradam 39 ।
hk transliteration by Sanscript