When Amavasya falls on a Monday, then it is called as the Somvati Amavasya and is regarded as an auspicious and fortunate day. On this particular day, devotees worship Lord Shiva and also offer prayers to their forefathers. Hindu women also observe a fast of Somvati Amavasya for the good fortune and longevity of their husbands.
The story of Somvati Amavasya states that once there was a Brahmin family whom a monk used to visit. In that family there were seven sons and one daughter, All the sons were married but the girl was still unmarried. The monk used to ask for alms and bless all the daughters-in-law to have a blissful conjugal life. But the parents of the daughter were worried and anxious that he never offered blessings to their daughter.
After a few days, the parents called a pandit and showed him the Kundali of their daughter. When the Pandit analyzed the horoscope of the girl, he informed the parents about an inauspicious and unfortunate yoga of her becoming a widow. They asked for remedial action. The Priest suggested the girl visiting an island named Singhal where she would find a washerwoman. If that washerwoman will apply Sindoor on her forehead along with the girl observing a strict fast of Somvati Amavasya, she can get rid of that inauspicious yoga.
The girl left for the island with one of her brothers. When they reached the seashore they had to figure out the ways how to cross the river. Thus, to find a way they sat under a tree and started to discuss their further journey. On that particular tree, a vulture had its nest and lived with its vulture chicks. But whenever the vulture gave birth, a snake used to eat those new-born in the absence of the vulture.
On that day also when the girl and her brother were sitting under the tree, the vultures went out and the infants were left alone in their nest. Before the snake could have killed them, the girl projected what could happen so she killed the snake in order to save the infants.
When the vultures returned they were so happy to see their children safe and alive. Hence, they helped the girl to reach the house of that washerwoman. The girl served the washerwoman with utmost dedication. With the penance and true devotion of the girl, the washerwoman got pleased and applied vermilion on her forehead.
After that, the girl left the place and was going back to her home. On her way, she stopped at a peepal tree, there she offered prayers, performed Parikrama around the tree and observed a Somvati Amavasya Vrat. When the fast was completed, with the effect of the fast and the Sindoor, the inauspicious yoga of the girl’s kundali was canceled.
Thus, since that particular day, devotees and mainly the Hindu women observe a fast of Somvati Amavasya to get blessed with a happy and blissful conjugal life and long life of their husbands.