Mahabharata 13.45.18

अत्र गाथा यमोद्गीताः कीर्तयन्ति पुराविदःधर्मज्ञा धर्मशास्त्रेषु निबद्धा धर्मसेतुषु

atra gāthā yamodgītāḥ kīrtayanti purāvidaḥdharmajñā dharmaśāstreṣu nibaddhā dharmasetuṣu

Our plain-language meaning of this verse is waiting for scholar review.