CHAPTER 4 · VERSE 40
Bhagavad Gita 4.40
अज्ञश्चाश्रद्दधानश्च संशयात्मा विनश्यति। नायं लोकोऽस्ति न परो न सुखं संशयात्मनः॥
The ignorant, faithless, and doubting person goes to ruin. For the skeptical soul, there is happiness neither in this world nor in the next.
Warns against chronic cynicism and doubt, which destroy peace of mind and prevent meaningful achievement.