The main deity of the Kojagra festival is Goddess Lakshmi. In the festival, Annapurna form of the Goddess is worshipped. According to legend, the Goddess Annapurna starts residing in the house from the night of Kojagra festival of Ashvin month. It is said that worshipping the Annapurna form of the Goddess sincerely in the night of Kojagra, there is happiness, prosperity and peace in the house and food crisis never comes in the house. With this belief, the Goddess Annapurna is worshipped in every house of the Maithil people in that night.[3]
The tradition of celebrating Kojagra has been going on from ancient times in the folk culture of Mithila. It was originated from the court of King Janaka in Mithila. According to legend, it was started by the King Janaka in Treta Yuga for his son-in-law Lord Rama. The first Kojagara was performed by the King Janaka for Lord Rama. It is said that the King Janaka performed the Kojagara puja for his son-in-law Rama and daughter Sita and sent betel (paan) leaves, bananas, makhana, and laddus as gifts for Rama. Since then, this festival of Kojagra has been celebrated in the Mithila region.[8]
The festival Kojagra is also related to the Samundra Manthan story of Puranas. In the Samundra Manthan (churning of the ocean) story as described in various Puranas written by Vedas Vyasa, Goddess Lakshmi emerged on the full moon day of Ashwin Shukla Paksha. There is a classical belief that this date should be specifically celebrated as the day for worshipping Goddess Lakshmi. According to Puranas, Lord Chandradeva and Goddess Lakshmi originated from the ocean, both are considered to be siblings. In the festival, Lord Chandradeva is also very important and worshipped. As evident from the Vedas and Ayurveda shows that the medicinal properties of all the trees and plants on earth are transmitted to them only through the moon rays. Similarly in the text Bhagawad Geeta, Lord Krishna, while preaching to Arjuna, said, "Nakshatranamah Shashi," meaning, "I am the moon, chief among all the stars."[7]
During this festival, which occurs after the end of the rainy season, the sky is completely clear and its rays, full of medicinal properties, fall directly on the earth. Based on these beliefs, Kojagara festival is celebrated with special importance on this date in Mithila.[7]