refers to a battle between gods and demons, and Indra (the king of the gods) was feeling depressed. At that time Indra’s wife Sachi took a thread, charged it with sacred verses or Mantras for protection and tied it on Indra’s hand. Through the strength of this thread Indra conquered his enemies. Since then till today this festival is celebrated.
In the Epics
In Mahabharata when Lord Krishna advised Yudhishtthir to tie the puissant Rakhi to guard himself against impending evils. Thus the Raksha Bhandhan symbolizes all aspects of protection of the good from evil forces. In the ancient Puranik scriptures, it is said that King Bali's stronghold had been the Raakhi. Hence while tying the rakhi this couplet is usually recited:
Yena baddho Balee raajaa daanavendro mahaabalah
tena twaam anubadhnaami rakshe maa chala maa chala
"I am tying a Rakhi on you, like the one on mighty demon king Bali. Be firm, O Rakhi, do not falter."
Rani Karnawati and Emperor Humayun
During the medieval era, Rajputs were fighting Muslim invasions. Rakhi at that time meant a spiritual binding and protection of sisters was foremost. A famous incident relates how rakhi by then had broken the religious barriers. When Rani Karnawati the widowed queen of the king of Chittor realised that she could in no way defend the invasion of the Sultan of Gujarat, Bahadur Shah, she sent a rakhi to Emperor Humayun. The Emperor touched by the gesture started off with his troops without wasting any time.
Alexander The Great and King Puru
The oldest reference to the festival of rakhi goes back to 300 B.C. at the time when Alexander invaded India. It is said that the great conqueror, King Alexander of Macedonia was shaken by the fury of the Indian king Puru in his first attempt. Upset by this, Alexander's wife, who had heard of the Rakhi festival, approached King Puru. King Puru accepted her as his sister and when the opportunity came during the war, he refrained from Alexander.