The glories of Pasankusa Ekadasi which occurs during the waxing moon in the month of September/October is described in Brahmavaivartha Purana in the conversation between Lord Krishna and Maharaj Yudhisthira.

Maharaj Yudhisthira said O Madhusudan what is the name of the Ekadasi that occurs during the waxing moon in the month of September/October. Please be kind and explain this to me.

Lord Krishna replied, O best of the Kings! The name of this Ekadasi is Pasankusa Ekadasi. Now please hear from me the glories of this Ekadasi which destroys all sins. Some people also call this Ekadasi as Papankusa Ekadasi. One should specially worship lord Padmanabha on the day of this Ekadasi. This Ekadasi awards a person the heavenly pleasures of liberation and his desired results. Just by chanting the holy names of Lord Vishnu one can attain all the piety of visiting all the holy places on the earth. If a conditioned soul in spite of indulging in various sinful activities due to illusion takes shelter and offers obeisances at the lotus feet of Lord Hari who is an expert in delivering the fallen souls then such a person does not have to go to hell.

Those Vaisnavas who criticize Lord Shiva and those Saivaites who criticize Lord Vishnu are both undoubtedly go to hell. The result one obtains by performing one thousand horse sacrifices or by performing one hundred Rajasuya sacrifices can not be equal to the one-sixteenth portion of piety one obtains by following this Ekadasi. There is no piety in this world that is equal to the piety earned by observing the Ekadasi. Therefore there is no other day as sanctified as this day of Ekadasi which is very dear to Lord Padmanabha.

O, King! As soon as a person fails to observe Ekadasis the sins begin to reside in his body. This Ekadasi awards its followers heavenly pleasure, liberation, freedom from diseased conditions, beautiful women, wealth, and food grains. O maintainer of the earth! If one observes this Ekadasi and remains awake on that night easily goes to the abode of Lord Vishnu.

Lord Krishna continued O best of the Kings! By observing the vow of this Ekadasi one can deliver ten generations from his mother’s family, ten generations from his father’s family, and ten generations from his wife’s family. If a person observes this Ekadasi either in his childhood or youthhood or in his old age he does not suffer the miseries of the material existence. One who strictly observes this Pasankusa or Papankusa Ekadasi then all his sinful reactions are eradicated and at the end of his life, he returns to the abode of Lord Vishnu. If a person gives away gold, sesame seeds, land, cow, food grains, water, umbrella, or shoes in charity then such a person does not have to go to the abode of Yamaraj. Anyone who spends his day without engaging in pious activities is like a dead man although he is breathing. His breathing is compared to the bellows of the blacksmith.

O best of the Kings! A person who digs well and lakes for the benefit of others donates land and houses and performs other pious activities such as performing sacrifices is not subjected to the punishment of Yamaraja. As a result of piety only people live long lives, become rich, take birth in high-class families and become deathless. The purport is that the direct result of observing Ekadasi is to attain devotional service to Krishna and the indirect result is to attain the temporary material benefits.

Source: ISKCON Desire Tree