Owing to austerity, impurities of the body and senses are eliminated and perfection gained.
Austerity or Tapas here implies the inner fire of purification that is caused by intense spiritual practice. That intensity with proper devotion towards the Divine, that Being that resides within all selves, will alchemically reduce to ashes all impurities within self in order to become a suitable vehicle for the Supreme Self to work through us.
Asceticism in its proper perspective is never self-torture nor does it sanction activities that are unnecessarily injurious to the body or mind. The human body is a temple and is not be destroyed nor desecrated nor abandoned. The human body is a place of worship (or worth-ship) where the mind may do internal Puja to the Deity.
Practicing austerity is practicing self-discipline, containing the body and reigning in the senses in order to focus our attention within. Burning away the dross in order to reveal the Inner Light, the reflection of self-perfection.
Austerity can be expressed in a multitude of ways as a self-discipline. It can be expressed as discipline of body, speech and mind. Non-harming of one’s own and others’ bodies, mita-ahara or moderation in eating, indifference to discomfort such as heat or cold. Practicing speech that is truthful, kind, necessary and pleasing. Self-restraint (overcoming compulsive and impulsive thoughts and actions), friendliness towards all without exception, even-mindedness in all circumstances and silence would be examples of mental austerity.
Practicing austerity of body, speech and mind will not only purify these vehicles of expression but also prepare the psyche as a suitable abode to realize the Self Within.