Pandavas Learn of Karna's Vow and Leave Dvaitavana
Spies bring word to the Pandavas in the Dvaitavana forest: Karna has vowed to kill Arjuna. Yudhishthira grows deeply anxious. He thinks of Karna's impenetrable armor, of all their difficulties, and decides they must leave the forest at once.
The news reached the Pandavas through spies: the son of the suta had taken a vow to kill Vijaya — Arjuna.
Prodded by the words of the messenger, the great archers began to think about the purport of those words. They could not find any happiness.
Yudhishthira, Dharma's son, was greatly anxious. He thought of the impenetrable armor that Karna possessed — the kavach (divine armor) and kundala (earrings) he had been born with, the very things that made him invincible in battle. He thought of all their difficulties. He had no peace of mind.
His intelligence, vast and clear, was full of such thoughts. He made a decision: they would leave the forest of Dvaitavana, infested with many predators and animals.
Meanwhile, Duryodhana ruled the earth with his brothers and the brave Bhishma, Drona, and Kripa. He consorted with Karna, the son of a suta, who was radiant in battle. King Duryodhana was always engaged in bringing pleasure to others. He honored the chief brahmanas and performed sacrifices with many donations. He did that which brought pleasure to his brothers. The brave one had decided that the fruits of wealth were to be enjoyed and given.
But in the forest, the Pandavas gathered their belongings. The vow had reached them. And they moved. Aranyaka Parva, Chapter 540