Mahabharata 2.13.35

2.13.35

anāramanto nighnanto mahāstraiḥ śataghātibhiḥ |
na hanyāma vayaṃ tasya tribhirvarṣaśatairbalam || 35 ||

Ourselves consisting of the eighteen younger branches of the Yadavas arrived at the conclusion that even if we struck our enemies continually with excellent weapons capable of taking the lives of the foes, we should still be unable to do anything unto him even in three hundred years. He hath two friends that are like unto the immortals, and in point of strength the foremost of all men endued with might. They are called Hansa and Dimvaka who are both incapable of being slain by weapons. The mighty Jarasandha, being united with them, becomes incapable, I think, of being vanquished by even the three worlds. O thou foremost of all intelligent men, this is not our opinion alone but all other kings also are of the same mind. There lived, O monarch, a king of the name of Hansa, who was slain by Rama (Valadeva) after a battle of eighteen days. But, O Bharata, hearing people say that Hansa had been killed, Dimvaka, O king, thought that he could not live without Hansa. He accordingly jumped into the waters of the Yamuna and killed himself. Afterwards when Hansa, the subjugator of hostile heroes, heard that Dimvaka, had killed himself, he went to the Yamuna and jumped into its waters. Then, O bull of the Bharata race, king Jarasandha, hearing that both Hansa and Dimvaka had been killed, returned to his kingdom with an empty heart. After Jarasandha had returned, O slayer of all foes, we were filled with pleasure and continued to live at Mathura.