SB 1.13.1
suta uvaca
viduras tirtha-yatrayam
maitreyad atmano gatim
jñatvagad dhastinapuram
tayavapta-vivitsitah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Sri Suta Gosvami said: While traveling on a pilgrimage, Vidura received knowledge of the destination of the self from the great sage Maitreya and then returned to Hastinapura. He became as well versed in the subject as he desired.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Vidura: One of the prominent figures in the history of the Mahabharata. He was conceived by Vyasadeva in the womb of the maidservant of Ambika, mother of Maharaja Pandu. He is the incarnation of Yamaraja. Being cursed by Manduka Muni, he was to become a sudra. The story is narrated as follows:
Once upon a time the state police caught some thieves who had concealed themselves in the hermitage of Manduka Muni. The police constables, as usual, arrested all the thieves and Manduka Muni along with them. The magistrate specifically punished the muni to death by being pierced with a lance. When he was just to be pierced, the news reached the king, and he at once stopped the act on consideration of his being a great muni. The king personally begged the muni’s pardon for the mistake of his men, and the saint at once went to Yamaraja, who prescribes the destiny of the living beings. Yamaraja, being questioned by the muni, replied that the muni in his childhood pierced an ant with a sharpened straw, and for that reason he was put into difficulty. The muni thought it unwise on the part of Yamaraja that he was punished for his childish innocence, and thus the muni cursed Yamaraja to become a sudra, and this sudra incarnation of Yamaraja was known as Vidura, the sudra brother of Dhrtarastra and Maharaja Pandu. But this sudra son of the Kuru dynasty was equally treated by Bhismadeva, along with his other nephews, and in due course Vidura was married with a girl who was also born in the womb of a sudrani by a brahmana. Although Vidura did not inherit the property of his father (the brother of Bhismadeva), still he was given sufficient state property by Dhrtarastra, the elder brother of Vidura. Vidura was very much attached to his elder brother, and all along he tried to guide him on the right path. During the fratricidal war of Kuruksetra, Vidura repeatedly implored his elder brother to do justice to the sons of Pandu, but Duryodhana did not like such interference by his uncle, and thus he practically insulted Vidura. This resulted in Vidura’s leaving home for pilgrimage and taking instructions from Maitreya.