Mbh 9.36.3a

Vaishampayana continued, "In a former Yuga, O king, there were three brothers that were ascetics. They were called Ekata, Dwita, and Trita, and all three were endued with effulgence like that of the sun. They were like Lords of the creation and were blessed with children. Utterers of Brahma, they had by their penances, acquired the privilege of attaining to the regions of Brahman (after death). With their penances, vows, and self-restraint, their sire Gautama, who was ever devoted to virtue, became highly and always pleased with them. Having obtained great joy in consequence of his sons, the adorable Gautama, after passing a long life here, went at last to the region (in the other world) that was fit for him. Those kings, however, O monarch, that had been the Yajamanas of Gautama, continued to worship Gautama's sons after the sire had proceeded to heaven. Amongst them, however, Trita, by his acts and study (of the Vedas), O king, became the foremost, even like his sire Gautama. Then all the highly blessed ascetics, characterised by righteousness, began to worship Trita as they had worshipped his sire Gautama before him. Once upon a time, the two brothers Ekata and Dwita thought of performing a sacrifice and became anxious for wealth. The plan they formed, O scorcher of foes, was to take Trita with them, and calling upon all their Yajamanas and collecting the needful number of animals, they would joyfully drink the Soma juice and acquire the great merits of sacrifice. The three brothers then, O monarch, did as settled. Calling upon all their Yajamanas for (obtaining) animals, and assisting them in their sacrifices and receiving a large number of animals from them, and having duly accepted them in gift in consequence of those priestly services which they rendered, those high-souled and great Rishis came towards the east. Trita, O king, with a cheerful heart was walking before them. Ekata and Dwita were in his rear, bringing up the animals.