The Brahmana, by fighting for the three other castes, does not commit sin. People say that there is no higher duty then renouncing life under such circumstances.
ब्राह्मणस्त्रिषु वर्णेषु शस्त्रं गृह्णन दुष्यति। एवमेवात्मनस्त्यागन्नान्यं धर्मं विदुर्जनाः॥