Mbh 6.91.1a

Sanjaya said, “During the progress, O king, of that fierce battle fraught with the slaughter of great heroes, Sakuni the glorious son of Suvala, rushed against the Pandavas. And so also, O monarch, Hridika’s son of the Satwata race, that slayer of hostile heroes, rushed in that battle against the Pandava ranks. And smiling the while, (several warriors on thy side), with a large number of steeds consisting of the best of the Kamvoja breed as also of those born in the country of the Rivers, and of those belonging to Aratta and Mahi and Sindhu, and of those of Vanayu also that were white in hue, and lastly those of hilly countries, surrounded (the Pandava army).[438] And so also with horses, exceedingly swift, fleet as the very winds, and belonging to the Tittri breed, (others encompassed that army). And with many horses, clad in mail and decked with gold, the foremost of their class and fleet as the winds the mighty son of Arjuna (viz., Iravat), that slayer of foes, approached the (Kaurava) force. This handsome and valiant son of Arjuna, named Iravat, was begotten upon the daughter of the king of the Nagas by the intelligent Partha. Her husband having been slain by Garuda, she became helpless, and of cheerless soul. Childless as she was, she was bestowed (upon Arjuna) by the high-souled Airavat. Partha accepted her for wife, coming to him as she did under the influence of desire. It was thus that that son of Arjuna was begotten upon the wife of another.[439] Abandoned by his wicked uncle from hatred of Partha, he grew up in the region of the Nagas, protected by his mother. And he was handsome and endued with great strength, possessed of diverse accomplishments, and of prowess incapable of being baffled. Hearing that Arjuna had gone to the region of Indra, he speedily went thither. And the mighty-armed Iravat, possessed of prowess incapable of being baffled, approaching his sire, saluted him duly, standing before him with joined hands.