The Prophets Sunnah has a great place in Islam, it is the second source of Islamic law after the Noble Quran. The research has tried to proof the authenticity of Sunnah, through the Quranic verses , hadith, and reason, there are also a consensus among the scholars of Islam. The research also prescribed the jobs of the The Prophets Sunnah, which are: to confirm laws of the Noble Quran, or to detail its abridged , or to restrict the absolute of Quran, or to private its general, or to interpret its ambiguous , or to legislate some laws that did not come in the Noble Quran. The research has shown that the enemies of Islam realized the importance of the Sunnah in the live of Muslims; So that they tried to raise suspicions about it, and reduce its legislative value, because the demolition of the Sunnah is the demolition of Islam itself. However, their efforts have been destroyed by our great scholars. There are two directions; one of them is Orientalists who questioned the Sunnah. Another direction is Quranists who denied the Sunnah.