Shiva Purana
एवं कुर्याद्यथाशक्ति क्रमाच्छिव पदं लभेत् । नित्यं रुचिकरं त्वेकं मंत्रमामरणांतिकम् ५१ ।
Doing thus according to one’s capacity one shall gradually attain Śiva’s region. It is the duty of every one to repeat a mantra pleasing to him every day till his death.
english translation
evaM kuryAdyathAzakti kramAcchiva padaM labhet । nityaM rucikaraM tvekaM maMtramAmaraNAMtikam 51 ।
hk transliteration by Sanscript