Sacrifice has been laid down as a duty of the three other castes, it has been laid down for the Shudra also, O Bharata, but he is not competent to utter svaha and svadha or any other Vedic mantra.
उक्तस्त्रयाणां वर्णानां यज्ञस्तस्य च भारत। स्वाहाकारवषट्कारौ मन्त्रः शूद्रे न विद्यते॥