13.4
तत्क्षेत्रं यच्च यादृक्च यद्विकारि यतश्च यत् । स च यो यत्प्रभावश्च तत्समासेन मे श्रृणु ॥
tatkṣetraṃ yacca yādṛkca yadkvikāri yataśca yat | sa ca yo yatprabhāvaśca tatsamāsena me śṛṇu ||
Translation
Hear from Me briefly what that field is, what its nature is, what its modifications are, from what it comes, who He (the Knower) is, and what His powers are.
Interpretation
Krishna signals a thorough account to follow: the field (its nature), its vikara (modifications — all the changes the body-mind undergoes), from what it arises, and the nature and powers of the Knower. This sets up one of the Gita's most systematic philosophical passages, drawing from the Sankhya system's analysis of human experience into field and Knower.