Srimad Bhagavadam 4.20.11
This verse describes how one can become liberated from material bondage. The first point is that one must know that the soul is different from his body. The soul is called dehī, or one who possesses the body, and the material body is called deha, or the embodiment of the soul. The body is changing at every moment, but the soul is fixed; therefore the soul is called kūṭa-stham. The change of body is enacted by the reactions of the three modes of nature. One who has understood the fixed position of the soul should not be disturbed by the incoming and outgoing interactions of the modes of material nature in the form of happiness and distress. In Bhagavad-gītā also, Lord Kṛṣṇa recommends that since happiness and distress come and go due to the interaction of the modes of nature on the body, one should not be disturbed by such external movements. Even though one is sometimes absorbed in such external movements, he has to learn to tolerate them. The living entity should be always indifferent to the action and reaction of the external body.
Lord Kṛṣṇa says in Bhagavad-gītā that the body, made of the gross physical elements (earth, water, fire, air and sky) and the subtle elements (mind, intelligence and ego), is completely different from the soul proper. One should therefore not be disturbed by the action and reaction of these eight gross and subtle material elements. The practical process to attain this stage of indifference is to execute devotional service. Only one who constantly engages in devotional service twenty-four hours a day can be indifferent to the action and reaction of the external body. When a man is absorbed in a particular thought, he does not hear or see any external activities, even though they are enacted in his presence. Similarly, those who are fully absorbed in devotional service do not care what is going on with the external body. That status is called samādhi. One who is actually situated in samādhi is understood to be a first-class yogī.
