This three-fold austerity, pursued with supreme attention by men, with no desire for any external reward therefrom, is held to be sāttvika.
Krishna first defined the austerities pertaining to the body, speech and mind. In pursuing these, there is again a threefold distinction – sāttvika, rājasa and tāmasa austerity. He defines the sāttvika first. How deftly does Krishna lead the seeker to the intricacies of the mind and intelligence, and make them sharper, more perceptive and evaluative!
Spirituality is the science and art of delving deep within the personality and effecting a thorough transformation and enrichment, whereby one becomes pure, benevolent and delightful. Rājasa and tāmasa traits are to be overcome by incorporating and intensifying the sāttvika ones. The process is amazingly enlightening – a very subtle psycho-intellectual analysis, filtering and enriching the inner personality.
Krishna says that all the three levels of austerity should be pursued with full care and concern, but with no expectation for any kind of external reward or gain therefrom. Then only the austerity will become sāttvika.