One verse

Bhagavad Gita 17.19

17.19

मूढग्राहेणात्मनो यत्पीडया क्रियते तपः | परस्योत्सादनार्थं वा तत्तामसमुदाहृतम् ||१७-१९||

mūḍhagrāheṇātmano yatpīḍayā kriyate tapaḥ . parasyotsādanārthaṃ vā tattāmasamudāhṛtam ||17-19||

mūḍha
foolish
grāheṇa
with endeavor
ātmanaḥ
of one’s own self
yat
which
pīḍayā
by torture
kriyate
is performed
tapaḥ
penance
parasya
to others
utsādana-artham
for the sake of causing annihilation
vā
or
tat
that
tāmasam
in the mode of darkness
udāhṛtam
is said to be

Penance performed out of foolishness, with self-torture or to destroy or injure others, is said to be in the mode of ignorance.