Bhagavad Gita: Chapter 17, Verse 19

मूढग्राहेणात्मनो यत्पीडया क्रियते तप: |
परस्योत्सादनार्थं वा तत्तामसमुदाहृतम् || 19||

mūḍha-grāheṇātmano yat pīḍayā kriyate tapaḥ
parasyotsādanārthaṁ vā tat tāmasam udāhṛitam

mūḍha—those with confused notions; grāheṇa—with endeavor; ātmanaḥ—one’s own self; yat—which; pīḍayā—torturing; kriyate—is performed; tapaḥ—austerity; parasya—of others; utsādana-artham—for harming; vā—or; tat—that; tāmasam—in the mode of ignorance; udāhṛitam—is described to be

mudha-grahenatmano yat pidaya kriyate tapah
parasyotsadanartham va tat tamasam udahritam

Translation

BG 17.19: Austerity that is performed by those with confused notions, and which involves torturing the self or harming others, is described to be in the mode of ignorance.

Commentary

Mūḍha grāheṇāt refers to people with confused notions or ideas, who in the name of austerity, heedlessly torture themselves or even injure others without any respect for the teachings of the scriptures or the limits of the body. Such austerities accomplish nothing positive. They are performed in bodily consciousness and only serve to propagate the grossness of the personality.