Bhagavad Gita · Chapter 3: The Path of Action
Bhagavad Gita 3.32
ये त्वेतदभ्यसूयन्तो नानुतिष्ठन्ति मे मतम् ।
सर्वज्ञानविमूढांस्तान्विद्धि नष्टानचेतसः ॥
ye tvetadabhyasūyanto nānutiṣṭhanti me matam | sarvajñānavimūḍhāṃstānviddhi naṣṭānacetasaḥ ||
But those who find fault with my teaching and do not follow it: know them to be deluded in all knowledge, without discernment, and lost.
Modern context
The other side is stated just as plainly. Those who find fault and never practise remain confused however much they know. The target is not honest doubt, which Arjuna himself voices freely. It is the cynicism that criticises from a distance so as never to have to try.