Verse
इदं ते नातपस्काय नाभक्ताय कदाचन ।न चाशुश्रूषवे वाच्यं न च मां योऽभ्यसूयति ॥
Never is this to be spoken by thee to one without askesis, not to one that is not devoted and not to him who does no service; nor yet to him who despises and belittles Me (lodged in the human body).
Gītā 18·67