mūḍha-grāheṇātmano yat pīḍayā kriyate tapaḥ
parasyotsādanārthaṁ vā tat tāmasam udāhṛitam||19||

Meaning : Austerity performed out of foolishness, to harm oneself, or to harm others — that is called tamasic (ignorant) austerity.