Lecture on Bhagavad Gita, Chapter 17, Texts 17-19 titled “The Top Then Brahmas” given by Prahladananda Swami.
Bhagavad-gita As It Is 17.17
sraddhaya paraya taptam
tapas tat tri-vidham naraih
This threefold austerity, performed with transcendental faith by men not expecting material benefits but engaged only for the sake of the Supreme, is called austerity in goodness.
Bhagavad-gita As It Is 17.18
tapo dambhena caiva yat
kriyate tad iha proktam
rajasam calam adhruvam
Penance performed out of pride and for the sake of gaining respect, honor and worship is said to be in the mode of passion. It is neither stable nor permanent.
Sometimes penance and austerity are executed to attract people and receive honor, respect and worship from others. Persons in the mode of passion arrange to be worshiped by subordinates and let them wash their feet and offer riches. Such arrangements artificially made by the performance of penances are considered to be in the mode of passion. The results are temporary; they can be continued for some time, but they are not permanent.
Bhagavad-gita As It Is 17.19
pidaya kriyate tapah
tat tamasam udahritam
Penance performed out of foolishness, with self-torture or to destroy or injure others, is said to be in the mode of ignorance.
There are instances of foolish penance undertaken by demons like Hiranyakasipu, who performed austere penances to become immortal and kill the demigods. He prayed to Brahma for such things, but ultimately he was killed by the Supreme Personality of Godhead. To undergo penances for something which is impossible is certainly in the mode of ignorance.