We read it in verse/ayat 44 of chapter 5 of the Holy Qur'an, where Allah Ta'ala says :--

   "WE SENT DOWN THE TORAH, WHEREIN IS LIGHT AND

    GUIDANCE, THEREBY THE PROPHETS THOSE WHO ARE 

    MUSLIMS, JUDGE FOR THOSE WHO ARE JEWS.." (5:44)

 The Shari'a of the Prophet Muhammad, Sallallahu alaihi Wasallam, has established the Shari'a of preceding generations. His Law is its roots, as he was sent " TO ALL PEOPLE "(34:28), while this belonged to no other Prophet." PEOPLE " extend from Adam to the last human being, and among them there have been Laws, so they are the Laws of Muhammad in the hands of his deputies. For he is sent "TO ALL PEOPLE", so all the Messengers are his deputies, without doubt, Sallallahu alaihi Wasallam.

 Thus when he came, he came with something great that comprised everything which was scattered among his deputies and something in addition. Hence Allah Ta'ala gave him the Mother of the Book, which comprised all the scriptures and books..