Aja, or Annada Ekadasi, is observed during the waning phase of moon (Krishna Paksha) in the month of Bhadrapada in
King Harishchandra was famous for his truthfulness and honesty. Once Sage Vashishta praised the truthfulness of Raja Harischandra but Sage Vishwamitra was not ready to accept it and he decides to test King Harishchandra. Vishwamitra vows to prove that Harischandra also lies.
As a result of Vishwamitra’s tests, King Harishchandra had to give up his kingdom and family and had to take refuge in Kashi. He becomes an undertaker in Kashi. But never lies. He always upheld truthfulness and proper code of conduct.
One day the great sage Gautama met King Harishchandra and the king narrated his sad tale to him. Sage Gautama advised King Harishchandra to observe Aja Ekadashi which has the power to remove all sins.
The King observed Aja Ekadashi and continued his firm faith in truthfulness.
Soon Sage Vishwamitra accepts his defeat and restores the kingdom, half of his power and all the glory to Harischandra. By the power of observing Aja Ekadasi, the King also got back his wife and his dead son became alive.
King Harishchandra ruled the kingdom for several years and finally got Moksha and reached the Vaikunta all with the influence of observing Aja Ekadashi.