BG Chap 13 - Knowledge as explained by the sages and the Vedas
Parāśara has described in Viṣṇu Purāṇa: ‘All the living entities are transcendental, although now they are in material bodies. All living entities, fallen in this flow of material guṇas, proceed through birth and death. They assume the guṇas by karma, and karma is accumulated through ignorance in all the unlimited entities. The pure ātmā is indestructible, peaceful, without those guṇas and superior to prakṛti. It has neither increase nor decrease in all bodies it assumes.
The Yajur Veda says that ether arose from the Lord. The Taittirīya Upaniṣad describes the five puruṣas consisting of food, prāṇa, mind, knowledge and bliss. Out of these, the first three—food, prāṇa and mind—involve the fields of activities of the living entities. They are material, comprising the kṣetra. The puruṣa composed of knowledge (vijñāna-maya-puruṣa) is the jīvātmā, the enjoyer of the field of body. He is the kṣetra-jña. Different from that is the ānanda-maya-puruṣa, the Supreme Lord, who is also kṣetra-jña.
The Brahma-sūtras also describe this knowledge in many places. Na viyad aśruteḥ: ether has no origin because it is not otherwise mentioned (2.3.1). Such verses describe the kṣetra or body. Nātmā śruteḥ: soul has no origin because of scriptural statements to that effect. (2.3.18). This describes the jīva. Parāt tu tac chruteḥ: the actions of the soul arise from the Supreme Lord according to scripture (2.3.39). This describes the Lord. The Vedānta-sūtra also describes the Supreme by saying, ānanda-mayo 'bhyāsāt: the Supreme Personality of Godhead is by nature full of joy. To enjoy His transcendental bliss, He expands into vijñāna-maya, prāṇa-maya, jñāna-maya and anna-maya. In the field of activities the living entity is considered to be the enjoyer, and different from him is the ānanda-maya. That means that if the living entity decides to enjoy in dovetailing himself with the ānanda-maya, then he becomes perfect. This is the real picture of the Supreme Lord as the supreme knower of the field, the living entity as the subordinate knower, and the nature of the field of activities.