Mbh 13.27.1

"'Yudhishthira said, "Thou O grandsire, art endued with wisdom and knowledge of the scriptures, with conduct and behaviour, with diverse kinds of excellent attributes, and also with years. Thou art distinguished above others by intelligence and wisdom and penances. I shall, therefore, O thou that art the foremost of all righteous men, desire to address enquiries to thee respecting Righteousness. There is not another man, O king, in all the worlds, who is worthier of being questioned on such subjects. O best of kings, how may one, if he happens to be a Kshatriya or a Vaisya or a Sudra, succeed in acquiring the status of a Brahmana? It behoveth thee to tell me the means. Is it by penances the most austere, or by religious acts, or by knowledge of the scriptures, that a person belonging to any of the three inferior orders succeeds in acquiring the status of a Brahmana? Do tell me this, O grandsire!"