After the great, unconquerable warrior falls and lies on his bed of arrows, this affects everybody and Karna remains no exception. He runs to meet him when Bheeshma is alone in the battle field, with tears in his eyes. The two were never in good talking terms. Bheeshma was angry with Karna because he was aware of him being a Kunteya and didn't want him to be with Duryodhan. Bheeshma didn't let him fight till he was the commander; he didn't want Karna to fight against his own brothers.
But when Bheeshma got the bed of arrows and he was resting in peace (Something he never got before), their emotions towards each other faced a change. No more anger, no more hatred. Karna stood near his grandfather's feet and his warm tears landed on those. Bheeshma slowly opened his eyes with much difficulty and noticed him. He embraced his grandson just like a father embraces his son, with tears flowing down his cheeks. Though they shared a bitter relation before and opposed one another, they never failed appreciating when needed.
"Karna, do you think that I hate you? No my child, I don't have any feeling of hatred towards you. I know you're a very mighty warrior. You're generosity is well known, you're equal to Arjuna in strength. But you are too vain about your strength, that's the reason I used to speak very harshly to you, to bring down your ego and pride. I've no anger left now".
Karna's voice was choked, he seeked forgiveness for his harsh and ignorant words and asked for blessings. Bheeshma told him he's a Kunteya and it isn't possible for the Kauravas to win the war. He tells him to join the Pandavas and advice Duryodhan to stop the war. Let all live with peace.
Karna states that a Suta brought him up when Kunti abandoned him. Duryodhan was the one who later supported him and now he can't turn these facts into lies. He shall fight for Duryodhan till the very end; he has pledged everything of him to Duryodhan. He further states that it's god' will for the destruction of the world, and Bheeshma too spoke about it. Nobody can change gods will.
Bheeshma replies, 'Karna! If you are unable to control your deep hate, I assent! Fight expecting to go to the heaven of the valiant. Give up your annoyance and grief and perform the duties of a kshatriya well and achieve a happy state of mind. Try your best to be righteous. Depend on your strength and bravery, leaving haughtiness. I tried my best for peace, but could not accomplish something. The victory will be for those who have dharma with them.' Karna salutes Bheeshma and goes away.