Mbh 3.300.2

“Surya said, ‘If O son, thou givest away thy ear-rings to the wielder of the thunder-bolt, O thou of mighty strength, thou shouldst also, for the purpose of securing victory, speak unto him, saying,--O thou of a hundred sacrifices, I shall give thee ear-rings under a condition.--Furnished with the ear-rings, thou art certainly incapable of being slain by any being. Therefore, it is, O son, that desirous of beholding thee slain in battle by Arjuna, the destroyer of the Danavas desireth to deprive thee of thy ear-rings. Repeatedly adoring with truthful words that lord of the celestials, viz., Purandara armed with weapons incapable of being frustrated, do thou also beseech him, saying, ‘Give me an infallible dart capable of slaying all foes, and I will, O thousand-eyed deity, give the ear-rings with the excellent coat of mail!’ On this condition shouldst thou give the ear-rings unto Sakra. With that dart, O Karna, thou wilt slay foes in battle: for, O mighty-armed one, that dart of the chief of the celestials doth not return to the hand that hurleth it, without slaying enemies by hundreds and by thousands!’”