A Shudra serves (the other classes); a Vaishya lives by trade and commerce; we live by massacre; and the wooden plate (profession of begging) has been selected by the Brahmanas.
शूद्रः करोति शुश्रूषां वैश्या वै पण्यजीविकाः। वयं वधेन जीवामः कपालं ब्राह्मणैर्वृतम्॥