Sharia law for Muslims is made up of four parts. First the Quran, which is the word of God as spoken by the Prophet Muhammad. Second are the Hadiths, the saying of the Prophet. These come from different men who knew him. Not all Muslims agree with the same Hadiths. Think of them like books of the New Testament and the apocrypha, some were accepted as canon and some not. Different Muslims have different canons. Third, are the Sunna or the Prophet’s actions. Again, told by different men who knew him and not all agree. Again, like the Gospels, the four do not always agree completely. Last is the Ijam, or reports of men who knew him. Because there is no central leader in Islam, like a Pope, there are different Sharia Laws for different areas.
Historically Speaking 