BG Chap 17 - Three types of austerity according to the modes
When the three kinds of austerity (of the mind, of the body and of the words) are undertaken with full faith, without longing for results but performed only for the sake of the Supreme with concentrated mind, they are said to be in goodness.
Austerity undertaken with the aim of getting verbal praise (words) such as ‘He is a great ascetic’, for the purpose of receiving bodily respect from others by having them standup when the person approaches, and for the purpose of gaining mental respect which would manifest in the future as gifts of money and other things, is austerity in the mode of passion. Its results are temporary if they appear at all, and uncertain that they would appear.
Austerity performed out of blind attachment and foolishness, inflicting pain on oneself, or for the purpose of harming or destroying others, is austerity in the mode of ignorance. Demons like Hiraëyakaçipu, and modern day worshippers of demigods engage in such austerity.