Muslim believes with all of his heart that the rituals and doctrines of Islam are entirely heavenly in origin and thus cannot have any earthly sources.
Middle East scholars have demonstrated beyond all doubt that every ritual and belief in Islam can be traced back to pre-Islamic Arabian culture. In other words Muhammad did not preach anything new. Everything he taught had been believed and practiced in Arabia long before he was ever born.
Jewish Sources of the Qur'an
Many of the stories in the Quran come from the Jewish Talmud, the Midrash, and many apocryphal works that already been written in 200 CE.
This was pointed out by Abraham Geiger in 1833, and further documented by another Jewish scholar, Dr. Abraham Katsh, of New York University, in 1954 (The Concise Dictionary of Islam, p. 229; Jomier, The Bible and the Quran -- Henry Regency Co., Chicago, 1959, 59ff; Sell, Studies, pp. 163ff.; Guillaume, Islam, p. 13).
1. The source of Sura 3:35-37 is the fanciful book called The Protevangelion's James the Lesser.
2. The source of Sura 87:19 is the Testament of Abraham.
3. The source of Sura 27:17-44 is the Second Targum of Esther.
4. The fantastic tale that God made a man "die for a hundred years" with no ill effects on his food, drink, or donkey was a Jewish fable (Sura 2:259ff.).
5. The idea that Moses was resurrected and other material came from the Jewish Talmud (Sura 2:55, 56, 67).
6. The story in Sura 5:30,31 can also be found in pre-Islamic works from Pirke Rabbi Eleazer, the Targum of Jonathan ben Uzziah and the Targum of Jerusalem.
7. The tale of Abraham being delivered from Nimrod's fire came from the Midrash Rabbah (see Suras 21:51-71; 29:16, 17; 37:97,98).
It must be also pointed out that Nimrod and Abraham did not live at the same time. Muhammad was always mixing people together in the Quran who did not live at the same time.
8. The non-biblical details of the visit of the Queen of Sheba (Saba) in Sura 27:20-44 came from the Second Targum of the Book of Esther.
9. The source of Sura 2:102 is no doubt the Midrash Yalkut (chapter 44).
10. The story found in Sura 7:171 of God lifting up Mount Sinai and holding it over the heads of the Jews as a threat to squash them if they rejected the law came from the Jewish book Abodah Sarah.
11. The story of the making of the golden calf in the wilderness, in which the image jumped out of the fire fully formed and actually mooed (Suras 7:148; 20:88), came from Pirke Rabbi Eleazer.
12, The seven heavens and hells described in the Quran came from the Zohar and the Hagigah.
13. Muhammad utilized the Testament of Abraham to teach that a scale or balance will be used on the day of judgment to weigh good and bad deeds in order to determine whether one goes to heaven or hell (Suras 42:17; 101:6-9).
Sabean Sources of the Qur'an
Muhammad incorporated parts of the religion of the Sabeans of Arabia into Islam (Encyclopedia off Islam (ed. Eliade), pp. 303ff.; International Standard Bible Encyclopedia, pp. 1:219ff.).
He adopted such pagan rituals as:
1. Worshiping at Kabah
2. Praying five times a day towards Mecca (Muhammad chose five of the same times the Sabeans prayed).
3. Fasting for part of a day for an entire month.
4. The Crescent Moon Symbol- The symbol of the worship of the moon god in Arabian culture and elsewhere throughout the Middle East was the crescent moon.
5. Allah - The Quraysh tribe into which Muhammad was born was particularly devoted to Allah, the moon god, and especially to Allah's three daughters who were viewed as intercessors between the people and Allah.
6. Astral Religions - In Arabia, the sun god was viewed as a female goddess and the moon as the male god. As has been pointed out by many scholars such as Alfred Guilluame, the moon god was called by various names, one of which was Allah! (Islam, p. 7).
Allah, the moon god, was married to the sun goddess. Together they produced three goddesses who were called "the daughters of Allah." These three goddesses were called Al-Lat, Al-Uzza, and Manat.
Eastern Religious Sources
Muhammad derived some of his ideas from Eastern religions such as Zoroastrianism and Hinduism. All of these things were in existence long before Muhammad was born.
Eastern and Asian Religions as Buddhism, Hinduiam, Yezdis, and Zoroastrianism.
The Quran records the following things which are ascribed to Muhammad but in reality were previously known stories now attributed to him for the first time (Sell, Studies, pp. 219ff.).
1. The story of a flying trip through seven heavens.
2. The Houries of paradise.
3. Azazil and other spirits coming up from Hades.
4. The "light" of Muhammad.
5. The bridge of Sirat.
6. Paradise with its wine, women, and song (from the Persians).
7. The king of death.
8. The peacock story.