Legend is that,after a long penace,Hiranyakashipu the king of demons was granted a boon by Brahma, that he can not be killed during day or night; inside the home or outside, not on earth or on sky; neither by a man nor an animal; neither by astra nor by shastra.

On getting the boon he became rude and attacked the Heavens and the Earth. He commanded that people should not worship the gods and start praying to him.

Hiranyakashipu's son, Prahlada, was a devotee of Lord Vishnu. In spite of threats from father, Prahlada continued worshipping Lord Vishnu. He was poisoned but the poison turned to nectar.He was put in a room with poisonous snakes,but still survived. All the attempts to kill him failed.

Finally, he ordered son Prahlada to sit on a pyre on the lap of his sister, Holika, who could not die by fire by virtue of a shawl which would prevent fire affecting the person wearing it. Prahlada obeyed his father's orders, and prayed to Vishnu to keep him safe.

When the fire started, everyone watched in amazement as the shawl flew from Holika, who then was burnt to death, while Prahlada survived unharmed, after the shawl moved to cover him. The burning of Holika is celebrated as Holi.