Shiva Purana
साधकः सिद्धमंत्रश्च निरस्तप्रतिबंधकः ॥ विश्वस्तः श्रद्धधानश्च कुर्वन्नाप्नोति तत्फलम् ॥ ९ ॥
An aspirant who has mastered the mantras overcoming the obstacles and who performs the rite with full confidence and conviction attains the fruit.
english translation
sAdhakaH siddhamaMtrazca nirastapratibaMdhakaH ॥ vizvastaH zraddhadhAnazca kurvannApnoti tatphalam ॥ 9 ॥
hk transliteration by Sanscript