Mbh 1.67.9b

And, as he grew up, he became very strong and excelled in all weapons. The first of all successful persons, he soon mastered the sciences. And when the intelligent one having truth for his strength recited the Vedas, there was nothing he would not then give to the Brahmanas. At that time Indra, the originator of all things, moved by the desire of benefiting his own son Arjuna, assumed the guise of a Brahmana, came to him, and begged of the hero his ear-rings and natural armour. And the hero taking off his ear-rings and armour gave them unto the Brahmana. And Sakra (accepting the gift) presented to the giver a dart, surprised (at his open handedness), and addressed him in these words, ‘O invincible one, amongst the celestials, Asuras, men, Gandharvas, Nagas, and Rakshasas, he at whom thou hurlest (this weapon), that one shall certainly be slain.’ And the son of Surya was at first known in the world by the name of Vasusena. But, for his deeds, he subsequently came to be called Karna. And because that hero of great fame had taken off his natural armour, therefore was he--the first son of Pritha--called Kama. And, O best of kings, the hero began to grow up in the Suta caste. And, O king, know thou that Kama--the first of all exalted men--the foremost of all wielders of weapons--the slayer of foes--and the best portion of the maker of day--was the friend and counsellor of Duryodhana. And he, called Vasudeva, endued with great valour, was among men a portion of him called Narayana--the god of gods--eternal. And Valadeva of exceeding strength was a portion of the Naga, Sesha. And, O monarch, know that Pradyumna of great energy was Sanatkumara. And in this way the portion of various other dwellers in heaven became exalted men in the race of Vasudeva, increasing the glory thereof.