Mbh 7.181.2a

“‘Vasudeva said, “If Jarasandha, and the ruler of the Chedis, and the mighty son of the Nishada king, had not been slain, they would have become terrible. Without doubt, Duryodhana would have chosen those foremost of car-warriors (for embracing his side). They had always been hostile to us, and, accordingly, they would all have adopted the side of the Kauravas. All of them were heroes and mighty bowmen accomplished in weapons and firm in battle. Like the celestials (in prowess), they would have protected Dhritarashtra’s sons. Indeed, the Suta’s son, and Jarasandha, and the ruler of the Chedis, and the son of the Nishada adopting the son of Suyodhana, would have succeeded in conquering the whole earth. Listen, O Dhananjaya, by what means they were slain. Indeed, without the employment of means, the very gods could not have conquered them in battle. Each of them, O Partha, could fight in battle with the whole celestial host protected by the Regents of the world. (On one occasion), assailed by Valadeva, Jarasandha, excited with wrath, hurled for our destruction a mace capable of slaying all creatures. Endued with the splendour of fire, that mace coursed towards us dividing the welkin like the line on the head that parts the tresses of a woman, and with the impetuosity of the thunder hurled by Sakra. Beholding that mace thus coursing towards us the son of Rohini hurled the weapon called Sthunakarna for baffling it. Its force destroyed by the energy of Valadeva’s weapon, that mace fell down on the earth, splitting her (with its might) and making the very mountains tremble. There was a terrible Rakshasa of the name Jara, endued with great prowess. She, O prince, had united that slayer of foes, and, therefore, was the latter called Jarasandha. Jarasandha had been made up of two halves of one child. And because it was Jara that had united those two halves, it was for this that he came to be called Jarasandha.