SB 3.5.21
bhavan bhagavato nityam
sammatah sanugasya ha
yasya jñanopadesaya
madisad bhagavan vrajan
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Your good self is one of the eternal associates of the Supreme Personality of Godhead for whose sake the Lord, while going back to His abode, left instructions with me.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Yamaraja, the great controller of life after death, decides the living entities’ destinies in their next lives. He is surely among the most confidential representatives of the Lord. Such confidential posts are offered to great devotees of the Lord who are as good as His eternal associates in the spiritual sky. And because Vidura happened to be among them, the Lord, while returning to Vaikuntha, left instructions for Vidura with Maitreya Muni. Generally the eternal associates of the Lord in the spiritual sky do not come to the material world. Sometimes they come, however, by the order of the Lord — not to hold any administrative post, but to associate with the Lord in person or to propagate the message of God in human society. Such empowered representatives are called saktyavesa-avataras, or incarnations invested with transcendental power of attorney.