Garuda tricks the snakes and Indra retrieves the amrita
Garuda returns to the snakes and places the amrita on kusha grass, demanding his mother's immediate freedom. The snakes agree and rush off to purify themselves. In that moment, Indra swoops in to reclaim the divine drink, leaving the snakes with nothing but grass to lick.
In great delight, Garuda told all the snakes, “I have brought you the amrita. I will place it for you on this kusha grass. O snakes! Drink it after bathing and purifying yourselves through rites. I have done what you asked. Therefore, as you promised, let my mother be freed from her slavery at this very instant.”
The snakes agreed and went off to have their baths.
The instant they turned away, Shakra (Indra) picked up the amrita and went off to heaven.
After bathing and purifying themselves through prayers and rites, the snakes joyfully returned to the place where the soma had been kept. They found they had been deceived. The vessel was gone. In desperation, they began to lick the darbha grass on which the soma had been placed.
Because of this act, the tongues of the snakes were split in two and became forked. And from that day, because of its contact with the amrita, the darbha grass became sacred.