Bhagavad Gita Chapter 13, Verse 4

तत्क्षेत्रं यच्च यादृक्च यद्विकारि यतश्च यत् | स च यो यत्प्रभावश्च तत्समासेन मे शृणु ||

tat kṣetraṁ yac ca yādṛk ca yad vikāri yataś ca yat sa ca yo yat prabhāvaś ca tat samāsena me śṛṇu

What the field is, of what nature it is, what its modifications are, from what it arises, who the knower is, and what his powers are—hear all this from Me in brief.

Krishna prepares to give a comprehensive description of the field. He'll explain what the field is (the body), its nature (material elements), its modifications (changes and transformations), its source (prakriti), the knower (consciousness), and the knower's powers (awareness, perception). This verse sets up the detailed explanation that follows. Most people never examine the field they're living in. They just experience it, identify with it, suffer from its changes. But understanding the field—what it is, how it works, where it comes from—is essential for recognizing the distinction between field and knower. You can't separate yourself from what you don't understand.