When the Pandavas were ruling over Indraprastha, it was decided that Yudhisthira would perform the rajasya yajna before being declared the lord of the earth. But before the yajna could be performed, it was necessary to kill Jarasandha who had imprisoned many Kshatriya kings.
Yudhisthira knew that it was not an easy task to defeat Jarasandha and began to think of ways and means to eliminate him. Seeing him worried, Bheema, the strongest of all the Pandavas, came forward with the suggestion, ?If Krishna, Arjuna and I were to combine our strength together and fight Jarasandha, we will be able to get rid of him.?
But Yudhisthira refused to agree to the suggestion as he feared that all three of them would lose their lives at the hands of Jarasandha.
So they all turned to look at Krishna who came forward and assured Yudhisthira that he would give all his support to Arjuna and Bheema and protect them in their fight against Jarasandha. Very reluctantly Yudhisthira agreed to let them go and fight Jarasandha.
So the three of them got dressed as simple Brahmins and went to Jarasandha'scourt. Jarasandha, on seeing the three of them, immediately sensed that they were no ordinary Brahmins but persons of royal lineage. Anyhow, he asked them the purpose of their visit. The three replied, ?Your Majesty, we have come to defeat you in a combat.?
Jarasandha smiled and replied, ?How can I enter into a fight with learned Brahmins like you all??
At this Krishna revealed his true identity. Jarasandha mocked at them, ?Krishna, I will not fight a coward like you. Arjuna, you are too young and callow for me. I am, however, prepared to fight Bheema who would be a match to my strength.?
So Bheema and Jarasandha left for the arena where both fought with maces, fists and every possible vile they could employ. Their fight continued for 27 days but none won. As both were equal in strength, the combat was declared a draw. On the 28th day, they again entered the combat but this time somehow Bheema looked worried and tense. Krishna realised this and knowing Jarasandha'sweakness, picked up a piece of twig and split it into two, lengthwise. He threw the pieces in opposite directions.
Bheema noticed this and entered the fray with renewed vigour. At the crucial moment, when Bheema noticed Jarasandha become lax, he caught him by the legs and pulled them apart with full might, splitting his body into two.
After killing Jarasandha, Krishna went to Jarasandha'sson and asked him to set free all the kings that his father had imprisoned. Yudhisthira'ssupremacy was accepted and Krishna returned to Indraprastha where Yudhisthira got the rajasya yajna performed to assert his authority over the kingdom.