Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 1
उद्धव उवाचतत: स आगत्य पुरं स्वपित्रो-श्चिकीर्षया शं बलदेवसंयुत: ।निपात्य तुङ्गाद्रिपुयूथनाथंहतं व्यकर्षद् व्यसुमोजसोर्व्याम् ॥ १ ॥
uddhava uvācatataḥ sa āgatya puraṁ sva-pitrościkīrṣayā śaṁ baladeva-saṁyutaḥnipātya tuṅgād ripu-yūtha-nāthaṁhataṁ vyakarṣad vyasum ojasorvyām
Śrī Uddhava said: Thereafter Lord Kṛṣṇa went to Mathurā City with Śrī Baladeva, and to please Their parents They dragged Kaṁsa, the leader of public enemies, down from his throne and killed him, pulling him along the ground with great strength.
King Kaṁsa’s death is only briefly described here because such pastimes are vividly and elaborately described in the Tenth Canto. The Lord proved to be a worthy son of His parents even at the age of sixteen years. Both brothers, Lord Kṛṣṇa and Lord Baladeva, went to Mathurā from Vṛndāvana and killed Their maternal uncle, who had given so much trouble to Their parents, Vasudeva and Devakī. Kaṁsa was a great giant, and Vasudeva and Devakī never thought that Kṛṣṇa and Balarāma (Baladeva) would be able to kill such a great and strong enemy. When the two brothers attacked Kaṁsa on the throne, Their parents feared that now Kaṁsa would finally get the opportunity to kill their sons, whom they had hidden for so long in the house of Nanda Mahārāja. The parents of the Lord, due to parental affection, felt extreme danger, and they almost fainted. Just to convince them that They had actually killed Kaṁsa, Kṛṣṇa and Baladeva pulled Kaṁsa’s dead body along the ground to encourage them.