SHAFAQNA- Nasr ibn Muzahim, in his book of Waq’a Siffin (one of the oldest books that were written nearly in the age of the Holy Imams), has reported that Habbah al-Arani, a companion of Imam Ali (A.S), to say:
When we landed in the region of al-Riqqah on our way of Siffin Battle, we camped near a monastery in which a Christian monk was engaged in worship. Seeing our soldiers, he came out of the monastery and headed for the commander of the faithful (A.S), saying:
“In this monastery, there is a book I have inherited from my ancestors; a book written by the disciples of Jesus during his lifetime. I would like to show the book to you.” The Imam said, “Go and bring it here.” The monk fetched the book and asked the Imam to give him permission to read it. Then, he began to read, “In the Name of Allah; Most Compassionate, Most Merciful. It is recorded in the Preserved Tablet that God will appoint from among the people of Mecca a prophet who will teach them the Book and Wisdom and will guide them to the right path and one of his signs is that he is neither rough nor bad-tempered. He is a man who when walking among people does not raise his voice nor does he compensate sin by sin, rather he forgives all. As for the community of that prophet, they are very thankful to God, praising Him under all conditions. Their tongues are tamed for the professing grandeur and glory of God. Their eyes will be tearful from fear of God. God will give victory to that Prophet over the arrogant. When he passes away, his community will be divided with rancor and enmity. They will have differences, then get together, and keep on living as long as God wills. A man from his community will cross by the Euphrates. This man will invite people to good and forbid them from evil. His judgment among people will be just, never issuing an unjust order. The world to him is less in value than the ashes blown away by wind on a stormy day. For him, death will be more pleasant than drinking of water by a thirsty person! He will fear God in hiding and give away in the path of Allah openly. He is not afraid of anyone who blames him on the straight path. Anyone who is living in these cities at that time and believes in that prophet will have heaven as his reward. And, everyone who understands this righteous servant crossing by the Euphrates must help him. After reading from the book, the monk said, “You are that righteous servant of God. I will come with you and will not leave you so that what will happen to you will happen to me. If you are martyred, I will be with you to be martyred.
Hearing this, the commander of the faithful (A.S) wept and said, “Thanks Allah; He has not forgotten me as He had my name among benefactors.” The monk accompanied the Imam and never left him until he was martyred in Siffin Battle. After the end of the battle, Imam Ali ordered the martyrs to be buried. Some were missioned to find the body of the monk and when they found it, the Imam stood at his head saying: “He is from us, Ahlul-Bayt.” Then, the Imam himself dug a grave for him and buried him as a Muslim.
(Source: Waq’a Siffin: 147)
Ref: Imam Reza.Network