The Event of Mubahala was a debate between the Islamic prophet Muhammad and the Christians of Najran, where the call was extended to the sons and women. Mubahala is a Qur'anic evocation of the occasion of an encounter between Muslims and Christians during Muhammad's lifetime. In this occasion Muhammad is instructed by Quran to issue a challenge to the visiting Christians of Najran.
The 'call' and 'challenge' is based on Islamic tradition, according to an ancient ceremony, of asking God to curse the party who is not speaking truthfully.
The Christians of Najran came to Medina claiming that Isa (Jesus) is divine and the son of Allah. In fact, they meant to determine whether Muhammad's claims were in accordance with the prophecies of their holy books. The event is recorded in several Hadith collections and is referred to in the Qur'anic surah Al Imran.
In such debates, each side would bring the most informed men, and hence the Christians of Najran were surprised when they saw "Ali, Fatima, Hasan and Husayn" accompanying Muhammad. It is seen as one of the merits of Ahl al-Bayt and is widely used by the Shia to prove that Muhammad, Ali ibn Abu Talib, Fatima, Hasan, and Husayn are Ahl al-Kisa and most prominent among his Ahl al-Bayt.
Al-Mubahalah' (Arabic: المباهلة) is derived from the Arabic word 'Bahlah' (curse), so the term 'Mubahala' means withdrawing the mercy from the one who lies or engages in falsehood. In Islamic tradition it refers to the ancient ceremony of mutually and formally calling God's curse down upon whichever of the two parties was not speaking truthfully on the occasion in Medina when the question as to the true identity of Messiah was put. It is an instance of Quran's critique of a central Christian doctrine, the doctrine of the Incarnation. This event of Mubahala might serve as a Quranic icon for the character of the Christian / Muslim dialogue which took place within the world of Islam after the Islamic conquest and after Christians in the occupied territories adopted the Arabic language. In this milieu Muslims challenged and critiqued major point of Christian faith, and Christians responded in defense of their defining doctrine and practice.