He wrote it down.
According to Islam, Muhammad is not a God, but a man.
The holy Prophet Hazrat Muhammad was the last of the holy Prophets sent by Almighty Allah (God). His source of information is the holy Qur'an that was revealed to him by Almighty Allah.
Muhammad was the last prophet from God.
Gabriel is the messenger of God, usually of revelational information.
We do not worship Muhammad. God forbid ! We only worship the One God. Muhammad was God's Messenger and Prophet, and His beloved servant. That is all.
Muhammad is Allah (God in English) messenger to call for the Islam religion per God revelation of Quran to him through the angel Gabriel (jibril). The founder of Islam is God (Allah in Arabic. Refer to question below for more information.
God (Allah in Arabic) is the Creator. Prophet Muhammad is God prophet per God revelation of Quran to him through the angel Gabriel (Jibril). However, it is to be emphasised that prophet Muhammad is a human who is inspired by God.
Islam has one god that has 100 names and that Muhammad is his last messenger. ps. the Muhammad I am talking about is (Not) Muhammad Ali
Prophet Muhammad conveyed to Muslims the Holy Quran that reflects real God words revelation to him through the angel Gabriel (Jibril). Accordingly all Islam teachings are per God revelation to prophet Muhammad and not per prophet Muhammad own choice or borrowing from other religions. The three religions are from same God. So, what is common and similar in the three religions are per God will and what is different is also per God will. Refer to questions below for more information.
The main information on Muslims is that they believe in God as the one and only one God with no partner, no companion, no son, no father, no associate, and no equivalence. Muslims are the followers of Islam. Islam per Torah God revelation to Moses is called Judaism. Islam per Bible God revelation to Jesus is called Christianity. Islam per Quran God revelation to Muhammad is called the same name Islam as Muhammad is the last God prophet and Quran is the last God holy book. The fundamentals of Islam per Quran God revelation to prophet Muhammad could be referred to in the questions below.
Prophet Muhammad (peace be upon him) died on the 8th of June 632 AD. However, Prophet Muhammad is not Islam religion founder. Islam religion is God religion per God Quran revelation to prophet Muhammad through the Angel Gabriel (Jibril) in year 610 AD. See question listed below for more information.
Islam religion per God Quran revelation to prophet Muhammad is founded by Allah (God in English and same God in Christianity and Judaism) and not prophet Muhammad (peace be upon him). Prophet Muhammad is the God Messenger and prophet who conveyed God message to his followers. Refer to related question below