A long time ago, there lived a king named, “Priyabrat” and his wife “Malini”. The king and his wife were living happily, but they were sad and miserable as they had no child. They decided to arrange a big Yagya with the help of Maharishi Kashyap to be blessed with a child. Due to the effects of the Yagya, Rani Malini got pregnant; however she delivered a dead child after nine months.
The king was very sad to know this, and decided to suicide. Suddenly, the Manas Kanya “Devsena” appeared and said, “I am Goddess Khashti and I’m an incarnation of the sixth part of the universe. If you worship me with pure mind and soul for six days, you would definitely be blessed with a child.” The king and her queen did the same and later they blessed with a very beautiful baby boy. Since then people started worshipping Chhathi Maiya (Shashti Goddess) and celebrating the Chhath Puja.
It is said that, Pandavas were in misery during their exile in the forest so much that Draupadi started crying on a day. Seeing this Yuddhisthira went to Dhoumya and asked for a solution to their misery.
Dhoumya Muni said, “Hey Yudhisthira, listen. The food grains that maintain life on the earth are the form of Sun God. Therefore, Lord Sun is their father. The people who worship Him on the sixth and seventh day of fortnight of Shukla Paksha in Kartik Mas with pure heart and chant the 108 names of Surya, get son, gems, wealth, endurance and wisdom.”
Being enlightened by Dhoumya Muni, Yudhisthira started worshipping Lord Sun and pleased him. Pleased by his devotions, Lord Sun appeared in front of Yudhisthira and gave him a magical copper vessel. Lord Sun told that this vessel would cook four types of food for them and will last till Draupadi, the wife of five Pandavas took her meal. This way, Pandavas came out of their misery. Hence, it is believed that by worshipping Bhagwan Surya during Chhath Pooja, one can fulfill all their desires and come out of all pain and suffering.