Muhammad's views on Christians were shaped through his interactions with them. Muhammad had a generally semi-positive view of Christians and viewed them as fellow receivers of Abrahamic revelation (People of the Book). However, he also criticised them for some of their beliefs. He sent various letters to Christian world leaders inviting them to "Submission to God, Islam". According to Islamic tradition, he interacted with Christians while in Mecca.
Book of Peace
The Ashtiname (Book of Peace) of Muhammad is a document which is a charter or writ ratified by Muhammad granting protection and other privileges to the followers of Jesus, given to the Christian monks of Saint Catherine's Monastery. It is sealed with an imprint representing Muhammad's hand. According to the monks' tradition, Muhammad frequented the monastery and had great relationships and discussions with the Sinai fathers.
An abridged version of the ashtiname is as follows:
Before the First Revelations
At the age of nine, or according to some sources twelve, Muhammad went to Syria with his uncle Abu Talib and had interactions with Christians. One important contact was with the Nestorian monk Bahira in Bosra, modern Syria who foretold to the adolescent Muhammad his future prophetic career. This narrative is found in multiple accounts of Syrian literature.
Another narrative found in the Sira of Ibn Sa'd shows that while Muhammad was working for Khadija, she had him go on a journey to Syria along with a man named Maysarah. Once they reached Bostra in the south of Syria, Muhammad was reported to have taken shelter underneath a tree. A monk named Nestor approached Maysarah asking him who was the man underneath the tree. Explaining to the monk who he was, Nestor quickly responded, "None other than a Prophet is sitting beneath that tree."
Waraqah ibn Nawfal was a Nestorian monk, first cousin to Muhammad's wife Khadija, and Mecca's priest or preacher according to some sources. He was the first man to tell Muhammad that he was a prophet based on the first revelation he received in the cave of Hira.
Byzantines
According to traditional Islamic sources, in 628 Muhammad sent a letter to Heraclius inviting him to Islam. The text of the letter to Heraclius (), reads as follows:Islamic sources say that after the letter was read to him, he was impressed by it and he gifted the messenger of the epistle with robes and coinage. Alternatively, he also put it on his lap. Later reportedly he wrote to a certain religious official in Rome to confirm if Muhammad's claim of prophethood was legitimate, and, after receiving the reply to his letter, called the Roman assembly saying, "If you desire salvation and the orthodox way so that your empire remain firmly established, then follow this prophet," to the rejection of the council. Heraclius eventually decided against conversion but the envoy was returned to Medina with the felicitations of the emperor. Some historians disagree with this account, arguing that there is no evidence outside of Islamic sources suggesting that Heraclius had any knowledge of Islam.
In 629 according to tradition, Muhammad sent a force of 3,000 men to fight 100,000 Byzantines near Al Karak. The Battle of Mu'tah ended with a defeat of Muhammad's army. Subsequent sources present the battle as a Muslim victory given that most of the Muslim soldiers returned safely.
Ethiopians
According to the traditional view, members of the early Muslim community in Mecca faced persecution, which prompted Muhammad to advise them to seek refuge in Aksum. The earliest account is given by the 8th-century historian Ibn Ishaq:When the Quraysh learned that Muhammad's companions could safely practice their religion in the Aksumite kingdom, they decided to send a delegation to the Negus to demand the surrender of the fugitives. The delegation included Amr ibn Hishām. The Meccans appealed to the generals, arguing that the Muslim migrants were "foolish youths" who had invented a new religion, the likes of which neither the Meccans nor the Aksumites had heard of, and that their relatives were asking for their return. Najashi, the king, granted them an audience and asked if they had with them anything which had come from God. One of the Muslims, Jafar, then recited a passage from the Quran's Surah Maryam (). When the king heard it, he exclaimed: "Verily, this and what Jesus brought (the Gospel) has come from the same source of light". He then affirmed that he would never give up the Muslims.