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

idaṁ te nātapaskyāya nābhaktāya kadāchana na chāśhuśhruṣhave vāchyaṁ na cha māṁ yo ‘bhyasūtayi

Never is this to be spoken by thee to anyone who is without asceticism, nor without devotion, nor to one who desireth not to listen, nor yet to him who speaketh evil of Me.

In plain words: Krishna warns Arjuna not to share this teaching with people who have no self-discipline, no devotion, no wish to listen, or who speak badly of Krishna.