Bhagavad Gita Chapter 13, Verse 20

प्रकृतिं पुरुषं चैव विद्ध्यनादी उभावपि | विकारांश्च गुणांश्चैव विद्धि प्रकृतिसंभवान् ||

prakṛtiṁ puruṣaṁ caiva viddhy anādī ubhāv api vikārāṁś ca guṇāṁś caiva viddhi prakṛti-saṁbhavān

Know that both material nature (prakriti) and the enjoyer (purusha) are beginningless. Know that modifications and qualities are born from material nature.

Krishna clarifies the relationship between prakriti (material nature, the field) and purusha (the enjoyer, the knower). 'Prakṛtiṁ puruṣaṁ caiva viddhy anādī ubhāv api'—know that both material nature and the enjoyer are beginningless. Both are eternal—the field and the knower exist eternally. 'Vikārāṁś ca guṇāṁś caiva viddhi prakṛti-saṁbhavān'—know that modifications and qualities are born from material nature. The field's changes, qualities, and modifications come from material nature. The knower is separate—it's the witness of these modifications, not the modifications themselves. This distinction is crucial: the field (prakriti) is eternal in its nature, but its modifications are temporary. The knower (purusha) is eternal and unchanging. When you understand this, you recognize that both field and knower are eternal, but the field's modifications are temporary. The knower remains constant while the field changes.