इदं ते नातपस्काय नाभक्ताय कदाचन।
न चाशुश्रूषवे वाच्यं न च मां योऽभ्यसूयति।।18.67।।
18.67 This (that I have taught) you should not ever be taught to one who is devoid of austerities and to one who is not a devotee; also, neither to one who does not render service, nor as well to one who cavils at Me.
18.67 I have taught you this most secret doctrine. This should not be imparted by you to someone who has not practised austere disciplines. Never should this be taught to someone who is not devoted to Me and to you, the teacher (i.e., when you have to play the role of a teacher of this doctrine). The meaning is that it should not be taught by you to someone who, though practising austerities, is not a devotee and does not serve Me. It is also never to be taught to one who has no wish to listen, even though he is a devotee. Nor should it be imparted to one who traduces Me, that is, who - when My nature, glories and attributes are described - discovers defects in them. The differences of case (from ablative to nominative form) is to teach that the last one is the most despicable character.
Idam te naatapaskaaya naabhaktaaya kadaachana; Na chaashushrooshave vaachyam na cha maam yo’bhyasooyati.
idam—this; te—by you; na—never; atapaskāya—to those who are not austere; na—never; abhaktāya—to those who are not devoted; kadāchana—at any time; na—never; cha—also; aśhuśhrūṣhave—to those who are averse to listening (to spiritual topics); vāchyam—to be spoken; na—never; cha—also; mām—toward me; yaḥ—who; abhyasūyati—those who are envious
