Shiva Purana
अनाचारवतां पुंसामविशुद्धषडध्वनाम् ॥ अनादिष्टो ऽपि गुरुणा मन्त्रो ऽयं न च निष्फलः ॥ ६४ ॥
This mantra is not ineffective even if it is not properly imparted by the preceptor. It is not ineffective even in the case of persons not caring for good conduct and who have not purified the six paths.
english translation
anAcAravatAM puMsAmavizuddhaSaDadhvanAm ॥ anAdiSTo 'pi guruNA mantro 'yaM na ca niSphalaH ॥ 64 ॥
hk transliteration by Sanscript