SB 1.16.5

śaunaka uvāca
kasya hetor nijagrāha
 kaliṁ digvijaye nṛpaḥ
nṛdeva-cihna-dhṛk śūdra-
 ko ’sau gāṁ yaḥ padāhanat
tat kathyatāṁ mahā-bhāga
 yadi kṛṣṇa-kathāśrayam
Word for word: 
śaunakaḥ uvāca — Śaunaka Ṛṣi said; kasya — for what; hetoḥ — reason; nijagrāha — sufficiently punished; kalim — the master of the Age of Kali; digvijaye — during the time of his world tour; nṛpaḥ — the King; nṛ-deva — royal person; cihna-dhṛk — decorated like; śūdrakaḥ — lowest of the śūdras; asau — he; gām — cow; yaḥ — one who; padā ahanat — struck on the leg; tat — all that; kathyatām — please describe; mahā-bhāga — O greatly fortunate one; yadi — if, however; kṛṣṇa — about Kṛṣṇa; kathā-āśrayam — related with His topics.
Translation: 
Śaunaka Ṛṣi inquired: Why did Mahārāja Parīkṣit simply punish him, since he was the lowest of the śūdras, having dressed as a king and having struck a cow on the leg? Please describe all these incidents if they relate to the topics of Lord Kṛṣṇa.
Purport: 

Śaunaka and the ṛṣis were astonished to hear that the pious Mahārāja Parīkṣit simply punished the culprit and did not kill him. This suggests that a pious king like Mahārāja Parīkṣit should have at once killed an offender who wanted to cheat the public by dressing like a king and at the same time daring to insult the purest of the animals, a cow. The ṛṣis in those days, however, could not even imagine that in the advanced days of the Age of Kali the lowest of the śūdras will be elected as administrators and will open organized slaughterhouses for killing cows. Anyway, although hearing about a śūdraka who was a cheat and insulter of a cow was not very interesting to the great ṛṣis, they nevertheless wanted to hear about it to see if the event had any connection with Lord Kṛṣṇa. They were simply interested in the topics of Lord Kṛṣṇa, for anything that is dovetailed with the narration of Kṛṣṇa is worth hearing. There are many topics in the Bhāgavatam about sociology, politics, economics, cultural affairs, etc., but all of them are in relation with Kṛṣṇa, and therefore all of them are worth hearing. Kṛṣṇa is the purifying ingredient in all matters, regardless of what they are. In the mundane world, everything is impure due to its being a product of the three mundane qualities. The purifying agent, however, is Kṛṣṇa.