In the Adi Parva of the Mahabharata, Karna challenges Arjuna at a tournament of the princes. Kripa objects to his birth: “Sons of kings never fight with men of inglorious lineage.” Duryodhana has Karna installed as king of Anga on the spot.
Karna asks: “what shall I give unto thee that may compare with thy gift of a kingdom?” Duryodhana answers: “I eagerly wish for thy friendship.” This is the Ganguli translation.