The Great Epic of the Bhārata dynasty 1.188.22

1.188.22

tato dvaipāyanastasmai narendrāya mahātmane |
ācakhyau tadyathā dharmo bahūnāmekapatnitā || 22 ||

"Vaisampayana continued, 'Then the illustrious Vyasa--the master Dwaipayana--rose, and taking hold of Drupada's hand led him to a private apartment. The Pandavas and Kunti and Dhrishtadyumna of Prishata's race sat there, waiting for the return of Vyasa and Drupada. Meanwhile, Dwaipayana began his discourse with illustrious monarch for explaining how the practice of polyandry could not be regarded as sinful.'"