What Happened between the Prophet of Islam and the Christians on the event of Mubahala?

These days are important days: the anniversary of the astonishing event of Mubahala, the sending down of Sura “Hal Ata” [al-Insan], the imminence of Muharram and the sensitive events that are taking place in the region.

Long ago in Arabia there was to be a debate between Mohammad (PBUH) and Christians of Najran. The debate was traditionally known as Mubahala, which occurred on the 10th year of AH. The prophet (pbuh) decided to participate in Mubahala and took up an invitation to meet with the Christians. During the event each side was to condemn the liar, asking God for punishment. However, when the Christian delegation saw the immaculate faces of the Prophet (PBUH) and his family (Ahlul Bait) including: Imam Ali, Lady Fatima Zahra, Imam Hassan, and Imam Hussain (PBUT), they were astonished; thus, they refrained from seeking condemnation towards the prophet and his household (PBUT). They knew that the prophet’s dua and his family’s duas (PBUT) would be accepted, so the Bishop of Najran asked the prophet (PBUH) for forgiveness and compromise. Following are the statements of Ayatollah Khamenei on this event.

These days are important days: the last ten days of Dhul-Hijja, the second half of that month. These are important days in terms of the history of Islam and the historical events of Islam. According to the well-known account: yesterday the 24th of Dhul-Hijja, was the day of Mubahila and the day of the revelation of the ayah about the wilayat of the Commander of the Faithful–God’s greetings be upon him. “Your wali is Allah, His Messenger, and those who believe–those who establish prayers and give charity while they bow down in worship [The Holy Quran, 5: 55].”
Today is also a day that marks the revelation of Sura “Hal Ata” [Sural al-Insan] of the Quran, and according to one account, today is the day of Mubahila. So, these are important days. Well, in the second half of the month of Dhul-Hijja, we have ‘Eid al-Ghadir which is a great ‘Eid and an important event in the history of Islam. Mubahila–which should be commemorated and is very significant–is, in fact, the manifestation of assurance, faith-based power, and reliance on legitimate truth. And this is what we always need. Today, we need the same faith-based power and the same reliance on our legitimate truth. This is because we are moving on the path of the truth. We should rely on this in the face of the enemies’ hostility, and we are, thankfully, doing so.
For this reason, there is, thankfully, a feeling of confidence among the public because the Iranian nation, public opinion, and the public orientations in our country, altogether, have a legitimate cause; they are moving in the right direction. Sura “Hal Ata” is also the manifestation of the blessing that exists during a sincere course of action. It is the manifestation of sincere sacrifice. Because of the sacrifice that the Ahl-ul Bayt made, Allah the Exalted sent down a sura for them: Sura “Hal Ata.” In addition to being a very important, valuable, and glorious historical event, it is a lesson. From the viewpoint of Allah, when sacrifice is accompanied by sincerity, it will lead to worldly and otherworldly rewards.

The above is Ayatollah Khamenei’s speech is delivered on Sep 6, 2018 which published in khamenei.ir.