Performing sacrifices (on behalf of others), teaching and acceptance of gifts are the (three) duties of the Brahmana. The duty of the Kshatriya is to rule and that of Vaishya is to tend (cattle).
याजनाध्यापनं विप्रेधर्मश्चैव प्रतिग्रहः। पालनं क्षत्रियाणां वै वैश्यधर्मश्च पोषणम्॥