The first time Hussein appears in a story about Christians, he is a small boy of about five. A delegation of Christian leaders from Najran, in southern Arabia, came to Medina to discuss with the Prophet the question that still divides the two faiths: who Jesus was.
The debate did not resolve. Then, the Qur’an records, the Prophet was told to propose something extraordinary: that both sides bring their own families, stand together, and ask God to judge between them. The Arabic word for this solemn appeal is mubahala.
According to a hadith in Sahih Muslim, when the verse came down the Prophet called the four people closest to him — his daughter Fatima, his cousin Ali, and his two grandsons, Hasan and Hussein — and said: “O God, these are my family.” The companion who remembered it, Sa‘d ibn Abi Waqqas, counted it among three things he had heard the Prophet say of Ali — any one of which, he said, was dearer to him than the finest red camels.
The Christians of Najran consulted among themselves and declined the challenge. The meeting ended instead in a treaty. In return for an annual tribute, the Najran Christians were promised the protection of their lives, lands, property and churches, and an assurance that no bishop, monk or priest would be removed from his office.