Since time immemorial Raksha Bandhan has been the symbol of spiritual bonding between brothers and sisters. Through this sacred bond (Rakhi), the brothers take oath to protect their sisters and sisters pray for the safety and well being of their brothers. Rakhi is supposed to protect the brothers from all impending evils.
During his invasion of the Indian subcontinent, in 326 BC, Alexander
was confronted, for the first time, by the heroism of the brave king,
Porus (the Indian ruler of the north western region). It is said that
the wife of the great conqueror approached king Porus with the sacred
thread (Rakhi) to ensure the safety of her husband, Alexander. As Porus
had accepted the bond of Rakhi, he promised to cooperate with Alexander
in his Indian venture. This is the oldest event associated with Raksha