Mbh 1.139.3a

“Seeing him, Karna left his bow and impelled by filial regard bowed down his head still wet with the water of inauguration. And them the charioteer, hurriedly covering his feet with the end of his sheet, addressed Karna crowned with success as his son. And the charioteer embraced Karna and from excess of affection bedewed his head with tears, that head still wet with the water sprinkled over it on account of the coronation as king of Anga. Seeing the charioteer, the Pandava Bhimasena took Karna for a charioteer’s son, and said by way of ridicule, ‘O son of a charioteer, thou dost not deserve death in fight at the hands of Partha. As befits thy race take thou anon the whip. And, O worst of mortals, surely thou art not worthy to sway the kingdom of Anga, even as a dog doth not deserve the butter placed before the sacrificial fire.’ Karna, thus addressed, with slightly quivering lips fetched a deep sigh, looked at the God of the day in the skies. And even as a mad elephant riseth from an assemblage of lotuses, the mighty Duryodhana rose in wrath from among his brothers, and addressed that performer of dreadful deeds, Bhimasena, present there, ‘O Vrikodara, it behoveth thee not to speak such words. Might is the cardinal virtue of a Kshatriya, and even a Kshatriya of inferior birth deserveth to be fought with. The lineage of heroes, like the sources of a lordly river, is ever unknown. The fire that covereth the whole world riseth from the waters. The thunder that slayeth the Danavas was made of a bone of (a mortal named) Dadhichi. The illustrious deity Guha, who combines in his composition the portions of all the other deities is of a lineage unknown. Some call him the offspring of Agni; some, of Krittika, some, of Rudra, and some of Ganga. It hath been heard by us that persons born in the Kashatriya order have become Brahmanas. Viswamitra and others (born Kshatriyas) have obtained the eternal Brahma.