The slaying of Jarasandha, King of Magadha, is described in the Shanti Parva section of the Mahabharata. Krishna, Bhima, and Arjuna travel to Magadha and challenge Jarasandha to a life and death kind of duel.
Jarasandha accepted the challenge and opted to fight Bhima. For 26 days, they fought daily in the arena for two and a half to three hours, till both were fully exhausted. Bhima tried every tactic of fighting but he could not kill Jarasandha. On the 27th day when they were fighting, Bhima looked at Krishna and asked, “What should I do?” Krishna picked up a leaf and tore it into two. Bhima instantly knew the way by which Jarasandha could be killed. He placed one leg on Jarasandha’s left leg and tore him into two.
Jara, the Jungle Goddess, had created Jarasandha by uniting the two halves of a divided-son born to King Brihadratha. There was only one way by which Jarasandha could be killed: the two halves of his body had to be ripped apart. After Jarasandha’s death, Krishna, Bhima, and Arjuna did not usurp his Kingdom of Magadha. They installed his son Sahadeva on the throne and then departed from the kingdom. In the Mahabharata war, Sahadeva fought on the side of Krishna and the Pandavas, the killers of his father.
The notion that the throne should go to the rightful heir has been part of the Hindu tradition since the Vedic period. When a king defeated another kingdom and killed its ruler, in most cases he allowed the next person in the legitimate line of succession to occupy the defeated kingdom’s throne.