The Mahabharata - pg. 257 - (Karna speaks)

"What you have said, dear mother, is contrary to dharma. If I swerve from the path of duty, I shall have done myself much more hurt than any that an enemy might inflict on me in the battle-field. You deprived me of all that was my birthright as a khshatriya when you threw me, a helpless babe, into the river; and now, you talk to me of my duties as a kshatriya. You denied me the motherly love which blesses all life and now, thinking of your other children's good, you tell me this story. If I now join the Pandavas, will not the world proclaim that I have done so out of fear? I have eaten the salt of Dhritashhtra's sons, won their confidence as their champion and enjoyed all the consideration and kindness they showed me; and now you want me - when the battle is about to be joined - to be untrue to my salt and go over to the Pandavas. The sons of the Dhritarashtra look on me as the ark which will enable them to cross the deluge of war. I have myself urged them into this war. How can I desert them? Could there be blacker treachery and baser ingratitude? What in life, or beyond it, would be worth a price like that? Mother dear, I must discharge my debt - aye, with life, if necessary: otherwise. I shall be no better than a common thief purloining my food all these years. I shall surely use all my powers against your sons in this coming war. I cannot deceive you. Please forgive me."
"But yet," continued he, "I cannot have my mother plead completely in vain. Part Arjuna to me. Either he or myself must die in this war. I will not kill your other sons, whatever they may do unto me. Mother of warrior sons, you will still have five sons. Either I or Arjuna will survive this war, and with the other four sons, you will still have five."
When Kunti heard her first-born speak this firmly adhering to the kshatriya code, her heart was full of tumultuous and contrary feelings and, without trusting herself to speak, she embraced him and departed in silence.
"Who can go against what has been ordained?" she thought. "He has, at least, offered not to harm four of my sons. That is enough. May God bless him", and she returned home.