Bhagavad Gita Chapter 17, Verse 5

अशास्त्रविहितं घोरं तप्यन्ते ये तपो जनाः | दम्भाहंकारसंयुक्ताः कामरागबलान्विताः ||

aśāstra-vihitaṁ ghoraṁ tapyante ye tapo janāḥ dambhāhaṅkāra-saṁyuktāḥ kāma-rāga-balānvitāḥ

Those people who practice terrible austerities not prescribed in scriptures, endowed with hypocrisy, ego, desire, and attachment—they do so with force.

Krishna describes those who practice 'aśāstra-vihitaṁ ghoraṁ tapaḥ'—terrible austerities not prescribed in scriptures. These are extreme practices created out of personal will rather than spiritual wisdom. More importantly, these practitioners are 'dambhāhaṅkāra-saṁyuktāḥ'—endowed with hypocrisy (dambha) and ego (ahaṅkāra). They're also 'kāma-rāga-balānvitāḥ'—endowed with desire (kāma), attachment (rāga), and force (bala). This reveals the problem: when you practice austerities not based on scriptural guidance, you're driven by ego, desire, and attachment rather than wisdom. You're using force to achieve your goals, not understanding to guide your practice. This is the opposite of sattvic practice—it's driven by rajas (passion) or tamas (ignorance). Understanding this helps you recognize when your spiritual practices are driven by ego rather than wisdom.