The following was spoken by Suta Goswami and taken from the Book Ekadasi compiled by Krsna Balaram Swami. (please forgive any typos)
Benefits of observing Ekadasi:
Arjuna the son of Prtha asked the Lord O Janardana what are the pious benefits of complete fasting, eating only supper, or eating but once at midday on Ekadasi, and what are the regulations for observing the various Ekasasi days, Kindly narrate all this to me.
Please listen as I now describe the results obtained by one who observes Ekadasi in this way. Neither the merit one receives by taking a bath in the sacred place of pilgrimage known as Sankhodara, where the Lord killed the Sankhasura demon, nor the merit one receives upon seeing Lord Gadadhara directly is equal to one sixteenth of the merit one obtains by fasting on Ekadasi. It is said that by giving charity on monday when the moon is full, one obtains a hundred thousand times the results of ordinary charity. O winner of wealth, one who gives charity on the day of the sankranti (equinox), attains four hundred thousand times the ordinary result. Yet simply by fasting on Ekadasi one obtains all these pious results as well as whatever pious results one gets at Kuruksetra during an eclipse of the sun or moon. furthermore, the faithful who observes complete fasting on Ekadasi achieves a hundred times more merit than one who perfoms an Asvamedha yajna (horse sacrifice). One who observes just a single Ekadasi perfectly earns the same merit as one who feeds a hundred thousand mendicants each day for 60 thousand years. And a person who properly observes Ekadasi just once earns ten times more merit than a person who gives a thousand cows in charity to a brahmana learned in the Vedas.
A person who feeds just one bramacari earns ten times more merit than one who feeds ten good brahmanas in his own house. But a thousand times more merit than is earned by feeding a bramacari is acheived by donating land to a needy and respectable brahmana, and thousand times more than that is earned by giving away a virgin girl in marriage to a young well educated responsible man. Ten times more beneficial than this is educating children properly on the spiritual path, without expecting any reward in return. Ten times better than this however is giving food grains to the hungry. Indeed, giving charity to those in need is the best of all, and there never has been or ever will be a better charity than this. O son of Kunti, all the forefathers and demigods in heaven become very satisfied when one give food grains in charity. But the merit one obtains by observing a complete fast on Ekadasi cannot be measured. O Arjuna, best of the kurus, the powerful effect of this merit is inconceivable even to the demigods and half this merit is attained by one who eats only supper on Ekadasi.
One should therefore observe fasting on Lord Hari’s day either by eating only once at midday, abstaining from grains and beans; by eating only once in the evening abstaining from grains and beans or by fasting completely. The processes of staying in places of pilgrimage giving charity and performing fire sacrifice may boast only as long as Ekadasi has not arrived. Therefore anyone afraid of the miseries of material existence should observe Ekadasi. Thus I have described to you O Arjuna the best of all methods of fasting s you have inquired from Me.”