Dwadashi vrata

Once Agastya stayed as a guest in the palace of the king Bhadrashwa for a week. He praised the queen Kanthimati a lot. The king wanted to know the reason. Agastya told him that in her previous birth, the queen was a maid to a rich man. Once, during a Dwadashi during heavy rains, he asked her to ensure that none of the lamps in a temple stopped burning during the night. She managed to do it, and was hence born as a queen in her next birth. According to Vayupurana, the king and queen were happy to hear this and started observing the Dwadashi vrata from then.