SB 5.10.16
kas tvam nigudhas carasi dvijanam
bibharsi sutram katamo ’vadhutah
kasyasi kutratya ihapi kasmat
ksemaya nas ced asi nota suklah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
King Rahugana said: O brahmana, you appear to be moving in this world very much covered and unknown to others. Who are you? Are you a learned brahmana and saintly person? I see that you are wearing a sacred thread. Are you one of those exalted, liberated saints such as Dattatreya and other highly advanced, learned scholars? May I ask whose disciple you are? Where do you live? Why have you come to this place? Is your mission in coming here to do good for us? Please let me know who you are.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Maharaja Rahugana was very anxious to receive further enlightenment in Vedic knowledge because he could understand that Jada Bharata belonged to a brahmana family either by disciplic succession or by birth in a brahmana dynasty. As stated in the Vedas: tad vijñanartham sa gurum evabhigacchet. Rahugana was accepting Jada Bharata as a guru, but a guru must prove his position not only by wearing a sacred thread but by advancing knowledge in spiritual life. It is also significant that Rahugana asked Jada Bharata which family he belonged to. There are two types of families — one according to dynasty and the other according to disciplic succession. In either way, one can be enlightened. The word suklah refers to a person in the mode of goodness. If one wants to receive spiritual knowledge, he must approach a bona fide brahmana-guru, either in the disciplic succession or in a family of learned brahmanas.