It is a day which is similar to the one on which you shall be standing (before your Lord on the Day of Reckoning).
(via Darvish blog) On the day of Eid-ul-Fitr, Imam Ali, inheritor of gnosis and to whom goes back all sufi lineage to finally connect to Prophet Muhammad, delivered a sermon in which he said: 'O people! Verily this day of yours is the day when the righteous are awarded and the wretched are losers. It is the day when Muslims thank God for having given them the will, the strength and the endurance to observe the fast and obey His commandments during the holy month of Ramadan. It is not a festival related in any way to worldly affairs. It has no connection with any historical event nor is it related to the changes of seasons or cycles of agriculture.
