Bhagavad Gita
18.41

ब्राह्मणक्षत्रियविशां शूद्राणां च परन्तप | कर्माणि प्रविभक्तानि स्वभावप्रभवैर्गुणैः ||

brāhmaṇa-kṣatriya-viśāṁ śūdrāṇāṁ ca parantapa karmāṇi pravibhaktāni svabhāva-prabhavair guṇaiḥ

Translation

The duties of Brahmanas, Kshatriyas, Vaishyas, and Shudras are distributed according to the gunas arising from their own nature.

Interpretation

Krishna now applies the guna framework to social roles. The four varnas — Brahmana (teachers/priests), Kshatriya (warriors/administrators), Vaishya (merchants/agriculturalists), and Shudra (artisans/service-providers) — are not fixed by birth but by one's svabhava (intrinsic nature) which is itself shaped by guna-combination. This is the Gita's implicit critique of caste by birth: what matters is the quality of consciousness (gunas) and resulting natural aptitude, not hereditary accident. The varna system, properly understood, is a map of social functions arising from natural human diversity.