Surya Advises Karna on Indra's Bargain
Karna resolves to give his earrings to Indra, but Surya intervenes with a warning: Indra's true motive is to ensure Karna's death at Arjuna's hands. The sun god instructs Karna to bargain — exchange the earrings and armour for an invincible spear that will destroy his enemies. Only on those terms should he give Shakra what he wants.
Surya spoke to his son.
"O son! O immensely strong one! If you wish to give your beautiful earrings to the wielder of the vajra (thunderbolt), you should speak to him so that your victory is ensured. Because of your rule, you will have to give your earrings to Shatakratu. But as long as the earrings adorn you, you cannot be slain by any beings."
Karna already knew this. The kavach and kundala were not mere ornaments — they were his immortality, fused to his body from birth, the reason no weapon could touch his vital points. Without them, he would be as vulnerable as any other warrior.
"O son! Therefore, the slayer of the danavas (demons) wishes to ensure your destruction at the hands of Arjuna in battle and seeks to rob your earrings."
Surya laid it out plainly. Indra was not coming as a petitioner seeking a gift. He was coming as a father protecting his son — Arjuna, his own child through Kunti, the man who would face Karna on the battlefield of the coming war. Without the earrings, Karna could be killed. With them, he could not. The math was simple.
"With good and true words, you should propitiate Purandara, lord of the gods, who never deviates from his objective, again and again and tell him, 'O one with the thousand eyes! I will give you my earrings and my excellent armour if you give me an invincible spear that will destroy all my enemies.'"
Surya gave him the terms. Not a gift freely given — a trade. The earrings and armour in exchange for a weapon of equal power: a spear that would never miss, that would return to the hand after killing hundreds and thousands of enemies, that would give Karna the ability to destroy his foes in battle.
"O Karna! It is only under this rule that you should give Shakra your earrings. With the spear, you will be able to kill your enemies in battle. O mighty-armed one! The spear of the king of the gods is such that, without killing hundreds and thousands of enemies, it does not return to the hand."
Surya finished his counsel. Then he disappeared.
Karna now knew the terms. He knew what Indra wanted, and he knew what he could demand in return. The exchange would happen — that much was fixed. But the shape of it, the price, the weapon he would carry into the war to come — that was still his to negotiate. Aranyaka Parva, Chapter 583