Bhishma said A Brahmana may take his food from another Brahmana or from a Kshatriya or from a Vaishya but he must never take food from a Shudra.
भीष्म उवाच ब्राह्मणा ब्राह्मणस्येह भोज्या ये चैव क्षत्रियाः। वैश्याश्चापि तथा भोज्याः शूद्राश्च परिवर्जिताः॥