अशास्त्रविहितं घोरं तप्यन्ते ये तपो जनाः ।
दम्भाहङ्कारसंयुक्ताः कामरागबलान्विताः ॥ १७.५ ॥

कर्शयन्तः शरीरस्थं भूतग्राममचेतसः ।
मां चैवान्तःशरीरस्थं तान्विद्ध्यासुरनिश्चयान् ॥ १७.६ ॥

aśāstravihitam ghoram tapyante ye tapo janā: |
dambhāhaṅkārasamyuktā: kāmarāgabalānvitā: || 17.5 ||

karśayanta: śarīrastham bhūtagrāmamacetasa: |
mām caivānta:śarīrastham tānviddhyāsuraniścayān || 17.6 ||

Krishna adds:

Understand those people to be of demonic resolve and nature, who, resorting to methods not sanctioned in the scriptures, perform cruel austerities, full of hypocrisy and ego, driven by passions and desires. Such senseless people torture the bodily constituents and also the indwelling supreme presence.

Scriptures are the outcome of incomparably great search and research into human psychology and intelligence. The findings they set forth so fervently and lovingly are true and hence eternal. They have the supreme purpose of revealing to humanity the powers and potentials hidden in the mind, intelligence and heart.

Scriptural pronouncements are verily meant to inform, correct and help seekers in discovering their own insufficiencies and then make them strive wholesomely to redress these and attain heights of goodness, elevation and expansion. If such benevolent and benedictory scriptures are disregarded, the effects can only be colossally disastrous. Krishna wants to avoid such an eventuality. And so, he warns all concerned about the dangers befalling inattention to scriptures. He tells us to which extent can people be misled, if the place and purpose of scriptures is not evaluated or understood.

In the name of austerity, many wrong and harmful steps are taken up by virulent people. Fostering pride, egotism, coupled with ambition, possessiveness, the worst of austerities are taken up. And what is the outcome? Such austerities only stifle them. The ill-directed austerities only serve to torment the elemental body.

The austerity-mongers may persuade themselves to believe that such torturous austerities are necessary to please the respective deities. But, in reality, they have only one effect of self-torment and self-persecution. Claiming to propitiate the higher sources, they hurt, harm and injure the Indwelling Lord Himself. Whatever such people may adduce, they are to be regarded as villainous in their nature and resolve.

Either in religion or in philosophy and spirituality, nothing is implied calling for torturing oneself or another. Instead, it should be always a pursuit of harmless goodness, benignness and elevation. Bhagavad Gita emphasizes this point unambiguously.

Three-fold Austerity – Sāttvika, Rājasika and Tāmasika

Having defined śraddhā, attention, as three-fold, on the basis of the three guṇas, Krishna points out the manner in which delusion works in misguided seekers. He clearly denounces their passionate and hateful indulgences in the name of spiritual austerities. Krishna also categorizes eating and food preferences into Sāttvika, Rājasika and Tāmasika. This categorization he extends to include the sphere of Yajña, Dāna and Tapas in general.

Nothing, merely on the basis of its appearance, can be adjudged as good, benevolent or elevating. In human life, mind has greater place than the body and senses. More than what is being done, the attitude and aim that shape the actions are the important considerations. One is what his or her mind is.

Krishna has already stated: śraddhā-mayo’yam puruṣaḥ (man is what his śraddhā is). Sensory actions and indulgences bring their qualitative divisions in the mind. Krishna spells out the differences distinctly, though briefly. But understand that this is a spiritual classification. It has to be viewed accordingly.