Yudhishthira said: Common people say that fasting is TAPAS (penances). Is fasting, however, really so, or is penance something different?"
Bhishma said: People do regard fast, measured by months or fortnight or days, as penance. In the opinion, however of the good, such is not penance. On the other hand, fast is an impediment to the acquisition of the knowledge of the Soul. The renunciation of acts (that is so difficult for all) and humility (consisting in the worship of all creatures and consideration for them all) constitute the highest penance. That is distinguished above all kinds of penance.
He who betakes himself to such penance is regarded as one that is always fasting and that is always leading a life of Brahmacharya (celibacy). Such a Brahman will become a Muni always, a deity evermore, even if he lives in the bosom of a family. He will become a vegetarian always, and pure forever. He will become an eater always of ambrosia, and an adorer always of gods and guests. Indeed, he will be regarded as one always subsisting on sacrificial remnants, as one ever devoted to the duty of hospitality, as one always full of faith, and as one ever worshipping gods and guests.
Yudhishthira said: How can one practising such penance come to be regarded as one that is always fasting or as one that is ever devoted to the vow of Brahmcharya, or as one that is always subsisting upon sacrificial remnants or as one that is ever regardful of guests?
Bhishma said: He will be regarded as one that is always fasting if he eats once during the day and once during the night at the fixed hours without eating during the interval. Such a Brahman, by always speaking the truth and by adhering always to wisdom, and by going to his wife only in her season and never at other times, becomes a Brahmacharin (celibate). By never eating meat of animals not killed for sacrifice, he will become a strict vegetarian. By always becoming charitable he will become ever pure, and by abstaining from sleep during the day he will become one that is always wakeful. That Brahman who never eats till gods and guests are fed, wins, by such abstention, heaven itself.