Why Do We Tie a Rakhi for Raksha Bandhan?
Once upon a time, Lord Krishna had a cousin named Shishupala who was born with 3 eyes and 4 arms. It was predicted that these "deformities" would go away, as soon as he lay in the lap of a certain person. This person turned out to be none other than Krishna, of course. But it was also predicted that Shishupala would one day also die at the hands of the same person.
Upon learning Krishna would be his slayer someday, Shishupala's mother requested Krishna to pardon her son for the first 100 mistakes. (On a side note: Krishna had gotten into a fight with his brother-in-law, Rukmi, because he wanted his sister to marry Shishupala. Umm ya... awkward!)
Ever since Krishna and Rukmini eloped and got married, Shishupala hated him. So I guess it wasn't that hard for Shishupala to reach that quota of 100 offenses, after all.
So when Shishupala reached his 101st offense... Krishna whipped out his weapon of choice, Sudarshan Chakra (the spinning disc), and beheaded him.
So... what does all this have to do with Raksha Bandhan?
I'm finally getting to that.
Krishna cut his hand as he flung his chakra towards Shishupala. Draupadi, who was married to his cousins, the Pandav brothers, was basically like a sister to Krishna. She happened to see this altercation and immediately ran to Krishna's aid. She tore off a piece of her sari and tied it around Krishna's hand to stop the bleeding.
As she was tying the piece, Krishna blessed her by saying, "Akshayam" which means "may it be unending." Krishna asked her what he could offer her in return, to which she replied, "Just your promise to always protect me." Little did she know this blessing would come in handy soon enough...