The Brahmana acquires prosperity by holy living, the Kshatriya by prowess, the Vaishya by manly exertion, and the Shudra by service.
शौचेन लभते विप्रः क्षत्रियो विक्रमेण तु। वैश्यः पुरुषकारेण शूद्रः शुश्रूषया श्रियम्॥