Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 3
द्वैपायनादनवरो महित्वे तस्य देहज: ।सर्वात्मना श्रित: कृष्णं तत्परांश्चाप्यनुव्रत: ॥ ३ ॥
dvaipāyanād anavaromahitve tasya dehajaḥsarvātmanā śritaḥ kṛṣṇaṁtat-parāṁś cāpy anuvrataḥ
Vidura was born from the body of Vedavyāsa and was not less than he. Thus he accepted the lotus feet of Kṛṣṇa wholeheartedly and was attached to His devotees.
The history of Vidura is that he was born of a śūdra mother, but his seminal father was Vyāsadeva; thus he was not less than Vyāsadeva in any respect. Since he was born of a great father, who was supposed to be an incarnation of Nārāyaṇa and who composed all the Vedic literatures, Vidura was also a great personality. He accepted Kṛṣṇa as his worshipable Lord and followed His instructions wholeheartedly.