What proof did Muhammad have that he had the truth? What tangible proof did he have for the truth? The apostles had the death and resurrection of Jesus Christ among other things. What did he have? Actually, not much of anything. The contemporaries of Muhammad weren’t eyewitnesses to anything miraculous. When Muhammad was challenged to perform miracles to confirm that he was from God, he never took the challenge (Sura 3:181-184; 4:153; 6:8-9; 17:88-96). Instead, he said he was just a man (17:93) and implied that the Qur’an authenticated him as a prophet (17:88). But there are no clearly defined miracles recorded in the Qur’an. Miracles were only attributed to Muhammad by Muslims who lived 100-200 years after his death because Christians kept asking them for proof that Muhammad was a prophet. These miracle claims are not based on eyewitness testimony, and give every indication of being legendary. Several speak of trees moving or saluting Muhammad as he passed by. Mountains and wolves allegedly salute Muhammad as well. And other miracle stories seem to be variations of the miracles Jesus performed (e.g., turning water into milk, feeding a thousand by multiplying a small meal). These miracle stories are found in the Hadith, a later collection of Muhammad’s saying and doings.
The most reliable author of the Hadith, Al Bukhari, and a majority of Muslim scholars admit that most of Muhammad’s alleged miracles are not authentic.
So, if Muhammad wasn’t confirmed by miracles, then why did people follow him? They didn’t at first. He and his followers were kicked out of Mecca in AD 622, twelve years after he apparently got his first revelation. (Since Mecca was a polytheistic city filled with tributes to other gods, Muhammad’s message of monotheism was not well received by the local merchants who made their living off of the commerce associated with polytheism.) It wasn’t until Muhammad led several successful military conquests between 622 and 630 that he began to attract a large following. His popularity was greatly increased when he led raids on Meccan caravans and divided the booty from those raids with followers. He also took numerous wives, which helped solidify his base of support. In other words, Muhammad’s popularity resulted from his lucrative military victories that he shared with his followers, his astute political dealings, and his personal charisma rather than from any miraculous confirmation or truth.
The military aspect of Islam highlights another major difference between the origin of Christianity and the origin of Islam. Christianity began as a peaceful faith and was considered illegal for about the first 280 years of its existence (during which time it experienced its greatest growth). If you became a Christian in the Roman Empire before about 311, you might be killed for it.
By contrast, after a brief but unfruitful attempt to propagate his faith peacefully, Muhammad turned to military force to spread Islam. By 630, he had seized Mecca by force and had control of much of what is now the Saudi Arabian peninsula. His followers kept the military campaign across to Constantinople and through North Africa and almost into France.
So here’s the contrast: in the early days of Christianity, you might be killed for becoming Christian; in the early days of Islam’s growth, you might be killed for not becoming a Muslim. In other words, the spread of these two great monotheistic faiths couldn’t have been more different: Islam spread by use of the sword on others; Christianity spread when others used the sword on it.
But why does a religion spread when its adherents are persecuted, tortured, and killed during its first 280 years? (Those are not good selling points.) Perhaps there’s some very reliable testimony about miraculous events that proves the religion is true. How else can you explain why scared, scattered, skeptical cowards suddenly become the most dedicated, determined, self-sacrificing, and peaceful missionary force the world has ever known?
Information and most of the text from I Don’t Have Enough Faith to be an Atheist by Norman Geisler and Frank Turek