One day, the sisters beheld the celestial white horse Ucchaishrava flying in the sky. They entered into a wager about the colour of the horse’s tail. Vinata claimed that it would be white, while Kadru bet that the white horse had a black tail. They agreed that the loser of the wager would spend her life in servitude to the other sibling. Deciding to ascertain the colour of the tail the next day, the sisters returned home.
At home, Kadru requested her sons (snakes) to seek the horse overnight and attach themselves to the tail so that it would appear black during inspection. The snakes refused. Kadru cursed them and declared that they would be burnt in the fire of the yagna conducted by King Janamejaya. Terrified by this curse, the snakes decided to appease her and attached themselves to Ucchaishravas’ tail.
The next day the sisters went to inspect horse. Observing a black tail, Vinata accepted defeat and started serving Kadru.