The origin of Chhath Puja is not clear and ambiguous. As it is believed to be originated from Vedas, Epic Mahabharata and Ramayana. It was also believe that, it has Legend of King named Priyabrat and his wife Malini blessed with beautiful baby boy and they started worshipping Chhathi Maiya (Shashti Goddess) and celebrating Chhath Puja.
It is story of king named “Priyabrat” and his wife “Malini”. Both are living happily, but have no child. They decided for Maha Yagya with the help of Maharishi Kashyap. King’s wife Malini got pregnant and delivered dead child. With this the king loses hope of decided to give his life, 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 Queen agreed to worship and after thay are blessed with Beautiful baby boy.
It believes that it is originated form the ancient Vedas – Rigvedas contains hymns of worshiping the God Sun and describe about the ritual and exemplifies the similar Costumes. It describes the stringent worshiping of God Sun and frugality and abstinence Rituals. Chhaiti Maiya is also worship and knows as USHA in the Vedas, believe to be younger wife of the Surya, the Sun God.
This ritual also referred in the Sanskrit Epic poem in which Draupadi is described with observing the ritual similar to Chhath Puja today. During the exile in the forest of the Pandavas, Draupadi started crying as Pandavas were in misery. To get solution of their misery, Yuddhisthira went to Dhoumya.
Sage Dhoumya gave the solution and explained that “the Food grain are the form of the Sun god that helps I maintaining the life on the earth. Therefore, the Sum god is their father. The people who worship the sun god on the sixth and seventh day of fortnight of Shukla Paksha in Karthik Mas with pure hearth and Chant the 108 names of Lord Surya will blessed with son, gems, wealth and wisdom and bring prosperity.
After enlightened and recommendation by Sage Dhoumya, 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 trobles and also help in re-gain their kingdoms. Hence, it is believed that by worshipping Bhagwan Surya during Chhath Puja, one can fulfill all their desires and come out of all pain and suffering.
Also, In Mahabharat, karan, the son of Kunti and God Surya do daily worship of his father Sun and special puja during the month of Kartik in Shukla Paksha. Karan is also a King of Aang (Now known as Bhagalpur in Bihar). People living in that part of Bihar also start worshipping lord Sun.
The yogic or scientific history of Chhath Puja dates back to the Vedic times. The rishis of yesteryears used this method to remain alive without any external intake of food and were able to obtain energy from the sunlight. This was done through the rituals of the Chhath Puja.
In Ramayana, It is believed that after Completion of Banwas (Exile) of 14 Years, Lord Rama & Mata Sita had kept fast together and offered puja to the Lord Surya (The Sun God) in the month of Kartik (in between October and December) in Shukla Paksha. Since then Chhath Puja became the important and traditional festival in the Hindu religion.