When they met Jarasandha, he suspected that they were not ascetics.
So, Shri Krishna told him the truth and said,
" We have come for person to person combact with you. You can choose any one of us to fight single combat with you."
Jarasandha said, "Krishna! You are a cowherd and Arjuna is still very young. But Bheema is strong. Therefore, I am prepared to fight with him.”Bheema and Jarasandha were equally strong. The fight began. Neither gave in easily.
They fought with each other continuously for thirteen days.
On the fourteenth day, Jarasandha showed signs of exhaustion.
But Bheema did not show any signs of exhaustion.