The Day of Mubahalah commemorates a significant event in early Islamic history that ​occurred on the 24th of Dhul Hijjah in the 10th year after the Prophet Muhammad's ​migration to Medina (approximately 631-632 CE).

The Day of Mubahalah marks an occasion when Prophet Muhammad engaged in the ​form of a spiritual contest with a Christian delegation from Najran (a region in present-​day Saudi Arabia). The Christians and Muslims were in disagreement over the nature of ​Jesus -whether he was divine or a prophet.

To resolve this theological dispute, both parties agreed to participate in a ritual ​called "mubahalah," which is mutual appreciation. The idea was that both sides would ​bring their most beloved thing that each side had and earnestly pray for God to reveal the ​truth by cursing whichever side was wrong.

On the appointed day, Prophet Muhammad brought his closest family members: his ​daughter Fatima, his son-in-law Ali, and his grandsons Hasan and Hussein. This group is ​highly revered in Shia Islam and known as the Ahl al-Kisa (People of the Cloak).

According to Shia tradition, when the Christian delegation saw the conviction and ​confidence of the Prophet and his family, they declined to go through with the mubahalah, ​fearing divine punishment. Instead, they agreed to a peace treaty with the Muslims.

To easily understand the day of Mubahalah, here is a short animation: