Every action produces a reaction. Material activities bind one to the cycle of birth and death through karmic reactions. The Bhagavad-gita (3.5) teaches that no one can remain without action even for a moment, and (3.9) explains that action performed as a sacrifice for the Supreme purifies one. The Bhagavad-gita (3.27) states that all actions are performed by the modes of nature, and (4.14-17) describes how to transcend karmic reactions through understanding.