Bhai Dooj celebrates the bond between brothers and sisters. Where Raksha Bandhan centres on the brother's promise of protection, Bhai Dooj centres on the sister's prayer for her brother's long life and well-being, and on the brother visiting her home.
The name Yama Dwitiya links the day to Yama and his sister Yamuna. The tradition holds that a brother who receives tilak and a meal from his sister on this day is blessed with long life. It is an expression of love and hope, not a guarantee.
The day also brings married daughters and their brothers together after the busy Diwali days. In many families, brothers travel to their sisters' homes, so the day renews family ties across distances.
Yama and Yamuna were the children of Surya (the Sun) and Sanjna. After they grew up and went their separate ways, Yamuna invited her brother many times to visit her, but Yama, busy with his duties, could not come. At last, on Kartika Shukla Dwitiya, he arrived at her home.
Overjoyed, Yamuna welcomed him with an aarti, applied a tilak to his forehead and served him a meal she had cooked herself. Touched by her love, Yama offered her a boon. She asked that every year on this day he visit her, and that any brother who receives tilak and a meal from his sister on this day be blessed with long life. Yama granted the wish, and the day has been observed ever since.