Penances, knowledge of the Vedas, and birth in a pure family, these are the causes of the status which one acquires of a Brahmana. When one is possessed of these three qualities then does he coine to be called a twice born person.
तपः श्रुतं च योनिश्चाप्यतेद् ब्राह्मण्यकारणम्। त्रिभिर्गुणैः समुदितस्ततो भवति वै द्विजः॥