śraddhātrayavibhāgayoga - Verse śloka 19
śloka 19
mūḍhagrāheṇātmano yatpīḍayā kriyate tapaḥ |
parasyotsādanārthaṃ vā tattāmasamudāhṛtam ||17-19||
Translation
That austerity which is performed foolishly by tormenting oneself or for the destruction of others—that austerity is said to be Tamasic.