Bhagavad Gita Chapter 18 Verse 67
भगवद् गीता अध्याय 18 श्लोक 67

इदं ते नातपस्काय नाभक्ताय कदाचन।
न चाशुश्रूषवे वाच्यं न च मां योऽभ्यसूयति।।18.67।।



हिंदी अनुवाद - स्वामी तेजोमयानंद
।।18.67।। यह ज्ञान ऐसे पुरुष से नहीं कहना चाहिए? जो अतपस्क (तपरहित) है? और न उसे जो अभक्त है उसे भी नहीं जो अशुश्रुषु (सेवा में अतत्पर) है और उस पुरुष से भी नहीं कहना चाहिए? जो मुझ (ईश्वर) से असूया करता है? अर्थात् मुझ में दोष देखता है।।


Brahma Vaishnava Sampradaya - Commentary

This absolute essence and eternal conclusion should never  be  disclosed  to
those who are not devotees. Those who are not submissive.  Who  are  without
faith, who are not austere of uncontrolled senses and unclean mind. Who  are
not committed. Who are insincere. Who show disrespect to the  Vaisnavas  and
the spiritual master. These should  never  be  instructed  Srimad  Bhagavad-
Gita.

However if one is  sincere  and  trying  to  serve  the  Vaisnavas  and  the
Vaisnava spiritual  master  either  directly  as  an  aspiring  disciple  or
indirectly as a humble aspirant. Then this confidential  revelation  may  be
disclosed to them; if the Vaisnava  spiritual  master  perceives  that  they
have the potential to be a devotee. The word kadacana meaning  should  never
affirms the point that in absence of devotion to the  Supreme  Lord  one  is
not qualified to receive this confidential knowledge.  The  Shabdha  Nirnaya
scripture states that the  word  ca  can  be  used  as  to  one  or  as  the
conjunction and. Similarly in order to emphasize non-disclosure to  one  who
is envious or blasphemes the Supreme Lord or His  devotees  the  conjunction
ca has been utilised. One who in the pantheon of  devotees  is  envious  and
blasphemous is more evil then one who is not a devotee at all.