Bhagavad Gita 13.21

Pleasure and pain are the fruits of virtuous and vicious actions. The force of desire acts on the mind and the mind impels the senses to act to get the objects of desire. Good and evil actions proceed from Nature and lead to happiness or misery. Evil actions produce misery and sorrow. Virtuous actions cause happiness and joy. The soul is the enjoyer. The wife works and prepares nice, palatable dishes the huand silently enjoys the fruits of her labour. He sits ietly and eats them to his hearts content. Even so Nature works and the soul experiences the fruits of Her labour, viz., pleasure and pain. When harmony predominates, virtuous actions are performed. When there is a preponderance of Rajas, both virtuous and vicious actions are performed. When Tamas predominates, sinful, unlawful and unrighteous actions are done. In the place of Kaarana (कारण) which means cause, some read Karana (करण) which means instrument such as the five organs of knowledge, five organs of action, mind, intellect and egoism (thirteen principles located in the body).Karya The effect, viz., the physical body. The five elements which form the body and the five senses, and which form the senseobjects which are born of Nature come under the term effect. All alities, such as pleasure and pain and delusion which are born of Nature, come under the term instruments because these alities reside in the instruments, the senses. In the production of the body, the senses and their sensations Nature is said to be the cause. Thus Nature is the cause of Samsara. Sugarcane is the cause. Sugarcane juice, sugar and sugarcandy are the effects or modifications of sugarcane. Milk is the cause. Curd, butter and ghee (meleted butter) are the modifications of milk. Whatever is a modification of something is its effect, and that from which the modifications come is their cause. Nature is the source or cause of all modifications. She generates everything. The ten organs, mind and the five objects of the senses are the sixteen modifications or effects. Mahat (intellect) is born of Mulaprakriti. From Mahat Ahamkara (egoism) is born. Mahat is the effect of Mulaprakriti and the cause of Ahamkara. Therefore Mahat is called PrakritiVikriti. Mahat? Ahamkara and the five Tanmatras (rootelements of matter) are the seven PrakritiVikriti. Each of these is a modification of its predecessor and is in turn the cause of its successor. The five rootelements generate the five gross elements. They are the subtle elements. These seven are both Nature and modification (Prakriti and Vikriti), cause and effect, and are included under the term cause. The functions of the body, senses, lifeforce, mind and intellect are superimposed on the pure Self. So the ignorant man says I am black I am fat I am hungry I am angry I am deaf I am blind I am the son of so and so? I know? I am the doer? I am the enjoyer, etc. The intellect is very subtle. It is in close contact with the most subtle Self. The Consciousness of the Self is reflected in the intellect (Chidabhasa) and so the intellect which has the semblance of,the Consciousness feels I am pure consciousness or Chaitanya. I experience pleasure and pain. The attributes of the pure Self are superimposed on the intellect. There is mutual superimposition between the intellect and the Self? Nature and Spirit. This is the cause of Samsara. Purusha? Jiva? Kshetrajna and Bhokta are all synonymous terms. Purusha here referred to is not the Supreme Self. He is the conditioned soul, the soul subject to transmigration who experiences pleasure and pain. The Self or the Absolute is ever free from Samsara and is unchanging. Prakriti and Purusha are the cause of Samsara. Nature generates the body, lifeforce, mind, intellect and the senses. The soul experiences pleasure and pain. Samsara is the experience of pleasure and pain. The soul is the Samsarin. He is the experiencer of pleasure and pain. (Cf. XV.9)