Ekadashi as such falls on the 11th day of both Shukla paksha (bright side) and Krishna Paksha (Dark side) each month and is considered to be spiritually beneficial day by Hindus. Mohini Ekadashi falls on the eleventh day of Shukla Paksha of the auspicious Vaishaka month as per hindu calendar. This day is dedicated to Lord Vishnu. The name Mohini is derived from a tale where Lord Vishnu appeared in the form of Mohini to distract Danavas from Amrit extracted during Sagar Manthan so the Gods could claim it.
The importance of Mohini Ekadashi is recorded first in Suraya Purana. Its importance is narrated to Yudhistira by Lord Krishna himself. It is believed that Lord Vashista advised Lord Rama to observe fast on this particular day to be free from all sins, to remove obstacles and distress he experienced from the separation from Sita when Ravana abducted her.
According to another legend, there was a wealthy merchant “Dhanapala’ in Bhadravati city who was pious and kind. He worshipped Lord Vishnu. Known for his charity towards poor and needy, he spent a fulfilled life. However his son ‘Dhrstabuddhi’ grew up as a savage, greedy and cruel person and was thrown out of the house. Dhrstabuddhi soon resorted to threatening, robbery and stealing from people to live. He was caught by soldiers of the kingdom and sentenced to exile from the kingdom. Dhrstabuddhi then went off to live in a forest where he relied on killing animals to slake his hunger. He continued through the pain remembering his childhood, his life and ill conducts each day. One day he passed next to the ashram of Sage Kaundinya and was touched by the environment around it. There was a river next to the ashram and Sage was bathing in the river. On his way back, few drops of water fell from Sages body on to Dhrstabuddhi and he broke into tears remembering his sins. He shared his life story with the Sage and pleaded that he seeked forgiveness. The Sage advised him to fast on the day of Mohini Ekadashi for repentance. As directed Dhrstabuddhi observed fast and prayed to Lord Vishnu. He offered food and help to poor on this day to wash away all his sins.
Fasting on Mohini Ekadashi helps devotees to get moksha from the past sins. Preparations of the fast actually begins a day prior on Dashami where the devotees wake up, bathe with chandan and water and prepare their mind for fast. People observing fast should only have one meal and avoid salt on Dashami. On the day of Mohini Ekadashi, devotees get dressed in clean clothes after bathing, offer puja to Lord Vishnu and Lord Parshuram and meditate their names in their prayers. Few people fast even without drinking water while others do eat fruits and observe Jagraan singing devotional songs. The fast continues till the second half of the next day Dwashmi (twelveth day) after which one can eat a home cooked meal. Fasting on Mohini Ekadashi rid our souls from all the ill effects of our past misdoings, frees us from all worldly distractions and helps bringing peace and happiness to our lives.