The Event of Mubahala was a meeting between the Islamic prophet Muhammad and a Christian delegation from Najran (present-day Yemen), in the month of Dhu'l-Hijja, 10 AH (October 631, October 631-2, October 632-3), where Muhammad invoked a curse attempting to reveal who was lying about their religious differences. The initial effort was to invite the Najrani Christians to Islam and acknowledgement of Muhammad as a prophet. During religious discussions of similarities and differences, the topic of the divinity of ‘Īsā (Arabic: عِـيْـسَى, Jesus) arose.
It is advisable for them to refer to pious and well experienced scholars to
settle their disputes.
Mubahalah is a challenge between two parties
who have different claims and one of them knows that he is lying. So
in Mubahalah, both parties come to seek from Allah (SWT) jointly to
send His curse upon the liars. It is allowed under such circumstances.
The announcement of Ghadeer took place on 18th Thil Hijjah in the year 10 after Hijra. The Prophet Muhammad (SAWA) passed away on 28 Safdar year 11 after Hijra which is just 70 days after Ghadeer.
The Prophet (SAWA) did celebrate the announcement of Ghadeer in different ways like :
1. He asked every Muslim who was present ( men and women) to give allegiance to Ali (AS) as The master after the Prophet and as Ameerul Mo’mineen.
2. He asked all who were present to convey the message of Ghadeer to those who were not present.
3. The Prophet informed the Ummah that Ghadeer is the greatest Eid in Islam.
4. He celebrated Ghadeer by informing the Muslim Ummah that Islam was never complete but after the announcement of Ghadeer.( Chapter 5, Verse 3).
5. He celebrated Ghadeer by informing Muslim Ummah that fasting the day of Ghadeer has great reward. Even in Sunni books you find this Hadeeth of fasting the 18th of Thil Hijjah ( day of Ghadeer) narrated by Abu Hurayra from the Prophet (Al-Bidayah wal Nihayah, vol 7, Hadeeth Ghadeer Khum).
These are few examples from the Prophetic acts celebrating the greatest announcement of Ghadeer.
The event of Mubahala took place on 24th Dhu'l hijja 9 AH and the event of Ghadir Khumm took place almost a year later on 18th Dhu'l hijja 10 AH.
The Prophet (s) passed away within a few months of Ghadir Khumm. At the first anniversary of that event Abu Bakr was in power and unlikely to celebrate an event that would undermine his own rule.
When we recite Durood (Salawaat) we mention the Prophet Muhammad (SAWA) and his Progeny (Ahlul Bayt)(AS) and Hazrat Ali (AS) is the head of Ahlul Bayt (AS) after the Prophet (SAWA).
Imam Ali (AS) was brought in Mubahala as Nafs of the Prophet (SAWA) while Hasan (AS) and Husain (AS) where brought as the sons of the Prophet (SAWA).
Imam Redha (AS) when Al-Ma'moon asked him about he greatest tribute of Ali in Quran, said : Mubahala when Allah mentioned Ali as Nafs of the Prophet (SAWA).