Garuda wished to free his mother from bondage. The snakes told him that Vinata would be freed if Garuda brought them amrita (a life-giving drink) from heaven. After many adventures, Garuda did succeed in bringing the amrita from heaven. (These adventures are catalogued in the Mahabharata.) But instead of giving amrita to the snakes, Garuda tricked them into licking sharp-bladed kusha grass. That is how snakes came to have forked tongues and that is the reason why Garuda is anathema to the snakes.

One should not get the impression that all snakes are cursed. Snakes which are not ill-natured, do not bite good people, and stay away from those who know the Garuda mantra, are blessed. These snakes are permitted to bite individuals whose appointed lifespans on earth are over.