Sanskrit
ब्राह्मणक्षत्रियविशां शूद्राणां च परन्तप । कर्माणि प्रविभक्तानि स्वभावप्रभवैर्गुणैः ॥ ४१ ॥
brāhmaṇa-kṣatriya-viśāṃ śūdrāṇāṃ ca parantapa karmāṇi pravibhaktāni svabhāva-prabhavair guṇaiḥ
Translation
Of Brâhmanas, Kshattriyas, Vaishyas and Shûdras, O Parantapa, the duties have been distributed, according to the qualities born of their own natures.
Annie Besant · The Bhagavad-Gita, translated by Annie Besant (4th ed., 1922) — Wikisource · Public Domain
Explanation
This is the verse that names names: Brahmana, Kshatriya, Vaishya, and Shudra, duties “distributed” according to gunas “born of their own natures” (svabhava-prabhava). Worth being direct about what this text says and what it became — as stated, duty tracks temperament and guna-mixture rather than parentage, but this verse and its neighbors went on to anchor a hereditary caste order that assigned people’s stations by birth alone, a real and serious tension with any modern commitment to social mobility and equality that isn’t worth arguing away.