Eid of Al-Ghadir and Fasting in it

بسم الله الواحد القهار

Sheikh As-Saduq:

Reward of fasting in the day of Ghadir Khum

Narrated my father, may Allah bless him, saying: narrated to us Sa'd Ibn Abdullah from Ibrahim Ibn Hashim from Al-Qasim Ibn Yahya from his grandfather Al-Hasan Ibn Rashed from Abi Abdullah(عليه السلام), saying: “I once asked abu ‘Abd Allah(عليه السلام), saying, ‘I pray to Allah to keep my soul in service for your cause, is there any other Eid for the Muslims besides the two Eids?’ 

The Imam replied, ‘Yes, O Hassan, there is a greater and more important Eid than these two.’ 

I then asked, ‘When is such Eid?’ 

He replied, ‘It is the day when ’Amirul Muminin(عليه السلام) was appointed as the banner and lighthouse for people.’ 

I then said, ‘I pray to Allah to keep my soul in service for your cause, ‘When is this Eid?’ 

He replied: ‘Days repeat themselves and that is the 18th of Dhil Hijjah.’

I then said, ‘what then we should do on this day?’ 

He replied, ‘Fast, O Hassan, increase your appeal before Allah saying, “Grant salawat (favors and compensation to Mohammad and his family worthy of their services to Your cause).” Denounce before Allah those who oppressed them and usurped their right, because the prophets, may Allah grant them favors, would command the trustees to celebrate the day when they were appointed as executors of the will, as Eid.’ 

I then asked, ‘What happens if one fasts on such day?’ 

He replied, ‘Fasting on this day is equal to fasting for sixty months. And do not ignore fasting on the twenty-seventh of the month of Rajab. It is the day when prophet-hood came down up on Mohammad(صلي الله وعليه وآله). Fasting on this day is equal to sixty months of yours.’”

Footnote: its chain is Hasan like Sahih(authentic), its narrators are either trustworthy or praiseworthy.

Source: Thawab Al-A'maal, Vol. 1 Pg. 228-229