Once, Narada asked Lord Brahma:
"O Lord, which Ekadashi falls in the Krishna Paksha of the month of Magha, and what is its vrat (observance) method? Please kindly tell me."
Lord Brahma replied:
"O Narada, this vrat is very ancient, sacred, and capable of destroying all sins. There is no doubt that it bestows victory to kings who observe it."
During the Treta Yuga, when Lord Shri Ram reached the seashore with the intention to invade Lanka, he could not find a way to cross the ocean. He asked Lakshman:
"O son of Sumitra! How can this deep, terrifying ocean, filled with aquatic creatures, be crossed? I see no way by which we can pass it easily."
Lakshman replied:
"O Lord, you are the very creator of this universe—what can remain hidden from you? Just half a yojana from here is an ashram at Kumari Island where the ancient sage Bakdalabhya resides. Please go to that sage and ask him for guidance."
Lord Rama visited the sage’s ashram, paid his respects, and the sage happily inquired about the purpose of his visit. Lord Ram said:
"O great sage, I have come here with my army with the intention to attack Lanka. Please tell me a way by which this ocean can be crossed."
The sage Bakdalabhya replied:
"O Rama! In the Krishna Paksha of the month of Magha, there is a sacred Ekadashi known as 'Vijaya Ekadashi'. By observing this vrat, you will surely attain victory. You will be able to cross the ocean along with your army. Now listen carefully to the procedure of this fruitful vrat."
Vrat Vidhi (Procedure):
On the Dashami (tenth day), establish a Kalash (sacred pot) made of gold, silver, copper, or clay. Fill it with water, place fresh leaves in it, and on top of it install a golden idol of Lord Narayana.
On the day of Ekadashi, reinstall the Kalash, and worship it with mala (garland), sandalwood paste, betel nut, coconut, etc., in a special way.
Place seven types of grains and barley on top of the Kalash. Perform puja with incense, lamp, and various food offerings.
Sit before the Kalash, listen to or recite holy scriptures and katha (spiritual stories) throughout the day. Perform jagaran (night vigil) and keep a ghee lamp burning all night.
On the Dwadashi morning (twelfth day), take the Kalash to a holy waterbody and place it there. Worship it once again, and donate it along with the idol to a Brahmin. Offer other donations according to your ability.
"O Rama, observe this Vijaya Ekadashi vrat along with your army commanders sincerely. Doing so will surely grant you victory."
Lord Brahma concludes:
"Narada, upon hearing this, Lord Ram observed the Vijaya Ekadashi vrat as instructed by the sage. Because of the power of this vrat, he became victorious, killed Ravana in battle, conquered Lanka, and regained Sita.
O son, those who follow this vrat with devotion attain success in this world and their afterlife becomes auspicious as well. Reading or listening to this story grants the merit equal to performing a Vajapeya Yagna (a major Vedic sacrifice). That is why everyone should observe Vijaya Ekadashi vrat."