Every fairy tale becomes the 'greatest' thing in Shiism. They claim Eid al-Ghadeer is the greatest Eid of Allah!!
Taken from Shia website:
Imam Sadiq(as) said: Eid-e-Ghadeer is the greatest Eid of Allah(swt)
(Ref: Wasail ush shia, Vol 5, Pg 224)
Imam Jafar Sadiq (as) said: “Fasting on the day of Ghadeer is equivalent to fasting throughout the entire age of the world… It is the greatest festival of Allah. Allah has not sent any prophet but that he celebrated this day as Eid and was aware of its sanctity. It is known in the heavens as ‘The Day of the Famous Covenant’… You might think that Allah, the mighty and the majestic, has created a day more sacred than that. No, by Allah! No, by Allah! No, by Allah!"
(Complete hadees is not quoted here)
Source: Tahdhib Al Ahkam – Sheikh Toosi Vol.3 Pg.143
Source:
http://www.imamreza.net/eng/imamreza.php?id=9581More:
[…] یوم غدیر خم افضل اعیاد امتی.
امالی صدوق: 125، ح 8.
The day/’Eid of Ghadir is the MOST SUPERIOR of all Eids of the Ummah […]
(Amali Sadooq, Vol 8 , p)
عن الصادق علیهالسلام قال: هو عید الله الاکبر،و ما بعث الله نبیا الا و تعید فی هذا الیوم و عرف حرمته و اسمه فی السماء یوم العهد المعهود و فی الارض یوم المیثاق الماخوذ و الجمع المشهود. وسائل الشیعه، 5: 224، ح
On the authority of Al-Sadiq (peace be upon him) who said …
[‘Eid Al-Ghadir] is the GREATEST ‘EID OF ALLAH (‘Eidallah Al-Akbar!). Allah did not sent any of the Prophets except that they CELEBRATED on that day and acknowledged the greatness of this day and the name of it has been mentioned in the heavens and earth. (Wasa’el Al-Shi’a, Vol 5 p 224
Imam Ja’far as-Sadiq (a) was asked if there was Eid for Muslims besides Friday, Adha and Fitr. Imam replied, “Yes, there is one more Eid which is most great in holiness (a’dhamuha hurmatan).” The person asked him which Eid that was. Imam said: “It is the day (i.e. Ghadir) when the Messenger of Allah declared the Chief of the Believers (Ali) his vicegerent, saying: “Of whosoever I am the Mawlaa, ‘Ali is also his Mawlaa. And it is the 18th of Dhil-hijjah.”
http://sonsofsunnah.com/2012/04/12/verily-they-are-majoos-enemies-of-islam-eid-ghadir-nowrooz-and-omars-death-the-rafidite-holidays/