Dear Alakendu Das,

Here are some references from Pali Buddhist canons. 93rd, Assalāyana sutta and 98th, Vāseṭṭha sutta in Majjhimanikāya describe the the Buddha's attitude towards the cast system, 'all are the same by birth and differ by their deeds'.

http://metta.lk/tipitaka/2Sutta-Pitaka/2Majjhima-Nikaya/index.html

Kind regards,

Rev. J Dhammaloka

PhD student,
Department of Mathematics and Statistics,
University of Canterbury,

New Zealand.