sa tam maha-bhagavatam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
While Uddhava, the chief and most confidential amongst the devotees of the Lord, was going away, Vidura, in affection and confidence, questioned him.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Vidura was much older than Uddhava. By family relationship Uddhava was a contemporary brother of Krsna’s, while Vidura was as elderly as Krsna’s father Vasudeva. But although junior by age, Uddhava was much advanced in the devotional service of the Lord, and therefore he is described herein as the chief amongst the devotees of the Lord. Vidura was confident about this, and thus he addressed Uddhava in that higher category. That is the way of courteous dealings between two devotees.