Verses 14–16 turn to the important question of tapas or sadhana, the disciplines undergone for the sake of spiritual growth. The Gita holds that no lasting progress is possible on the spiritual path without self-discipline. The root of the word tapas is tap, to be hot or to suffer pain; and in fact tapas can also mean heat or suffering. When certain spiritual practices are mastered, they create a feeling of heat in the body, which is a sign of increased spiritual potency.
