Story of Ekādaśī

The eleventh day after a new moon or full moon day. The vrata observed on this day is called the Ekādaśī vrata. King Ambarīṣa observed very strictly and continuously the Ekādaśī Vrata to obtain the status of Indra. (See under Ambarīṣa). (Navama Skandha, Bhāgavata). This vrata would fetch food for the hungry and salvation for those who are in search of it. (Agni Purāṇa). The method of observing this vrata is detailed below:

Those who observe the Ekādaśī vrata should be on a regulated diet excluding meat and avoid sexual acts on the Daśamī day, the day preceding Ekādaśī. On both the Ekādaśī days in a month one should not take any food at all. The period which combines Ekādaśī with Dvādaśī (the twelfth day) is called Harivāsara because of the presence of Viṣṇu at that time. That is a good time for doing sacred yajñas. That day where there is only a small portion of Ekādaśī and the rest Dvādasī is the best day for yajñas. Trayodaśī (the thirteenth day) is good for breaking the fast. The day which merges Dvādaśī into Trayodaśī is the best day for breaking the fast. Do not observe the Vrata on a day which combines Daśamī with Ekādaśī. Hell is the result if one does so.

Completely abstaining from food on the Ekādaśī day you should take food on the Dvādaśī day. As you take your food you should pray like this: "Bhuṅkṣyehaṃ Puṇḍarīkākṣa śaraṇaṃ me bhavācyuta". (Oh, Puṇḍarīkākṣa, I am going to break my fast. Oh, Bhagavan, let you be my heaven). If an Ekādaśī comes on a Pūyaṃ—Puṣya—day in the bright half of the month that day should on any account be observed. That day would give the observer unlimited good result and that Ekādaśī is qualified as Pāpanāśinī (destroyer of all evils). When Ekādaśī and Dvādaśī happen to combine on a Tiruvoṇam (Śrāvaṇa) day the Ekādaśī is qualified as Vijayā. That day gives prosperity to devotees. It is also called Vijayā if an Ekādaśī comes in the month of Phālguna (March) on a Pūyaṃ (Puṣya) day. The wise extol this day as one promising crores of good effects. On the Ekādaśī day you should do Viṣṇu Pūjā which is productive of universal happiness. He who does so will acquire children and wealth in this world and attain Viṣṇuloka on death. (Chapter 178, Agni Purāṇa)