Mbh 3.298.2a

Vaisampayana said, “As thou askest me, O tiger among kings, I will relate that history unto thee! Do thou listen to my words, O best of the Bharatas! After twelve years (of their exile) had passed away and the thirteenth year had set in, Sakra, ever friendly to the sons of Pandu, resolved to beg of Karna (his ear-rings). And, O mighty monarch, ascertaining this intention of the great chief of the celestials about (Karna’s) ear-rings, Surya, having effulgence for his wealth, went unto Karna. And, O foremost of kings, while that hero devoted to the Brahmanas and truthful in speech was lying down at night at his ease on a rich bed overlaid with a costly sheet, the effulgent deity, filled with kindness and affection for his son, showed himself, O Bharata, unto him in his dreams. And assuming from ascetic power the form of a handsome Brahmana versed in the Vedas, Surya sweetly said unto Karna these words for his benefit, ‘O son, do thou O Karna, listen to these words of mine, O thou foremost of truthful persons! O mighty-armed one, I tell thee to-day from affection, what is for thy great good! With the object, O Karna, of obtaining thy ear-rings, Sakra, moved by the desire of benefiting the sons of Pandu, will come unto thee, disguised as a Brahmana! He, as Well as all the world, knoweth thy character, viz., that when solicited by pious people, thou givest away but never takest in gift! Thou, O son, givest unto Brahmanas wealth or any other thing that is asked of thee and never refusest anything to anybody. Knowing thee to be such, the subduer himself of Paka will come to beg of thee thy ear-rings and coat of mail. When he beggeth the ear-rings of thee, it behoveth thee not to give them away, but to gratify him with sweet speeches to the best of thy power. Even this, is for thy supreme good!