Adi Parva - Sambhava Parva 47

"Vaisampayana continued, 'There was amongst the Yadavas a chief named
Sura. He was the father of Vasudeva. And he had a daughter called Pritha,
who was unrivalled for beauty on earth. And, O thou of Bharata's race,
Sura, always truthful in speech, gave from friendship this his firstborn
daughter unto his childless cousin and friend, the illustrious
Kuntibhoja--the son of his paternal aunt--pursuant to a former promise.
And Pritha in the house of her adoptive father was engaged in looking
after the duties of hospitality to Brahmanas and other guests. Once she
gratified by her attentions the terrible Brahmana of rigid vows, who was
known by the name of Durvasa and was well-acquainted with the hidden
truths of morality. Gratified with her respectful attentions, the sage,
anticipating by his spiritual power the future (season of) distress
(consequent upon the curse to be pronounced upon Pandu for his
unrighteous act of slaying a deer while serving its mate) imparted to her
a formula of invocation for summoning any of the celestials she liked to
give her children. And the Rishi said, 'Those celestials that thou shall
summon by this Mantra shall certainly approach thee and give thee
children.' 'Thus addressed by the Brahmana, the amiable Kunti (Pritha)
became curious, and in her maidenhood summoned the god Arka (Sun). And as
soon as he pronounced the Mantra, she beheld that effulgent deity--that
beholder of everything in the world--approaching her. And beholding that
extraordinary sight, the maiden of faultless features was overcome with
surprise. But the god Vivaswat (Sun) approaching her, said, 'Here I am, O
black-eyed girl! Tell me what I am to do for thee.'

"Hearing this, Kunti said, 'O slayer of foes, a certain Brahamana gave me
this formula of invocation as a boon, and, O lord, I have summoned thee
only to test its efficacy. For this offence I bow to thee. A woman,
whatever be her offence, always deserveth pardon.' Surya (Sun) replied,
'I know that Durvasa hath granted this boon. But cast off thy fears,
timid maiden, and grant me thy embraces. Amiable one, my approach cannot
be futile; it must bear fruit. Thou hast summoned me, and if it be for
nothing, it shall certainly be regarded as thy transgression.'

"Vaisampayana continued, 'Vivaswat thus spoke unto her many things with a
view to allay her fears, but, O Bharata, the amiable maiden, from modesty
and fear of her relatives, consented not to grant his request. And, O
bull of Bharata's race, Arka addressed her again and said, 'O princess,
for my sake, it shall not be sinful for thee to grant my wish.' Thus
speaking unto the daughter of Kuntibhoja, the illustrious Tapana--the
illuminator of the universe--gratified his wish. And of this connection
there was immediately born a son known all over the world as Karna
accountred with natural armour and with face brightened by ear-rings. And
the heroic Karna was the first of all wielders of weapons, blessed with
good fortune, and endued with the beauty of a celestial child. And after
the birth of this child, the illustrious Tapana granted unto Pritha her
maidenhood and ascended to heaven. And the princess of the Vrishni race
beholding with sorrow that son born of her, reflected intently upon what
was then the best for her to do. And from fear of her relatives she
resolved to conceal that evidence of her folly. And she cast her
offspring endued with great physical strength into the water. Then the
well-known husband of Radha, of the Suta caste, took up the child thus
cast into the water, and he and his wife brought him up as their own son.
And Radha and her husband bestowed on him the name of Vasusena (born with
wealth) because he was born with a natural armour and ear-rings. And
endued as he was born with great strength, as he grew up, he became
skilled in all weapons. Possessed of great energy, he used to adore the
sun until his back was heated by his rays (i.e., from dawn to midday),
and during the hours of worship, there was nothing on earth that the
heroic and intelligent Vasusena would not give unto the Brahmanas. And
Indra desirous of benefiting his own son Phalguni (Arjuna), assuming the
form of a Brahmana, approached Vasusena on one occasion and begged of him
his natural armour. Thus asked Karna took off his natural armour, and
joining his hands in reverence gave it unto Indra in the guise of a
Brahmana. And the chief of the celestials accepted the gift and was
exceedingly gratified with Karna's liberality. He therefore, gave unto
him a fine dart, saying, 'That one (and one only) among the celestials,
the Asuras, men, the Gandharvas, the Nagas, and the Rakshasas, whom thou
desirest to conquer, shall be certainly slain with this dart.'

"The son of Surya was before this known by the name of Vasusena. But
since he cut off his natural armour, he came to be called Karna (the
cutter or peeler of his own cover).'"