Krishna tells Karna how unbearable an agony it must be for him not to participate in the Kurukshetra battle, especially when every kshatriya willingly joined the war just to prove their mettle. Since Karna could not fight until Bhishma died, the chances for Karna's participation were very slim. He suggests to Karna that he join the Pandavas, especially since they were his brothers, and then rule Hastinapura. Karna refuses flatly, citing his supreme love for Duryodhana.
Dritarashtra is lamenting his blindness that wouldn't let him participate in the war. His charioteer Sanjaya speaks to him consoling words when Sage Vyasa arrives there. Seeing Dritarashtra rue his blindness, Vyasa is willing to give him the power of sight to see the war, but Dritarshtra is unwillingness, since he has got used to his blindness, and doesn't have the strength of mind to see blood and gore. He then asks the sage to give this boon to Sanjaya, who would moderate and relate to him whatever transpires on the battle field.