For the good of Brahmanas and kine, and on occasions when mixture of castes takes place, even a Vaishya may take up weapons for his own safety.
गोब्राह्मणहितार्थं च वर्णानां संकरेषु च। वैश्यो गृह्णीत शस्त्राणि परित्राणार्थमात्मनः॥