Q. Is fasting on Ekasdashi one kind of Karma Kanda activity? Recently i have heard from one senior devotee narrating that by eating grains on Ekadashi, one will be getting sins. Hence, in order to avoid sins we are fasting and since it is not related to the Supreme Lord, Ekadashi can be one kind of karma kanda activity. Please clarify. Please give me quotes from the scriptures where it is mentioned that one has to fast from grains and beans on Ekadashi.

A.The reason why devotees fast on Ekadasi is because Lord Caitanya wanted it. Lord Caitanya is pleased when devotees follow Ekadasi fast.

In Caitanya-caritamrita, there is a section dealing with this topic. See Adi Adi-lila 15.8-11. Here Lord Caitanya instructs His mother Sacidevi to follow this fast.
If we do not follow this fast, we will get sins. That does not make this a karma-kanda ritual. By following karma-kanda rituals, one expects material rewards but devotees follow Ekadasi in order to obtain pure devotional service.