The Vat Savitri Puja – Vat Purnima festival is celebrated in honor of Savatri, the wife of Satyavan who brought her dead husband back to life. On this day married Hindu women observe a fast from sunrise to sunset and worship Savitri as the Goddess for the prosperity and longevity of their spouses.
Please find below the story of Savatri also known as Vat Savitri Vrat Katha :
The Puranas narrate the story of Savitri, who had lost Satyavaan, her husband. It has been foretold that Satyavan won’t live long. Even before her marriage, she was well aware that she would lose her husband a year after her marriage.
When Savitri saw Yama (God of Death) taking away her husband`s soul, she refused to give her beloved husband. Since, she was adamant, Yama offered her a boon. First, she asked for the lost sight of her blind father-in-law. Yama granted it to her. She then followed him as he took Satyavan’s body away. Yama offered her another boon. She now asked for her family`s lost empire and prosperity. This boon, too, was granted. But she was relentless, and continued to follow him. As they approached Yama’s abode, he offered her a final boon. She asked for a son. He granted it. She then asked him how it would be possible for her to beget sons without her husband. Yama was trapped and had to return soul of her husband to his body.