SB 10.57.26
uvasa tasyam katicin
mithilayam sama vibhuh
manitah priti-yuktena
janakena mahatmana
tato ’siksad gadam kale
dhartarastrah suyodhanah
Translation:
The almighty Lord Balarama stayed in Mithila for several years, honored by His affectionate devotee Janaka Maharaja. During that time Dhrtarastra’s son Duryodhana learned from Balarama the art of fighting with a club.