Difference between Prophet (Nabi) and Messenger (Rasul)

There is a minor difference between a Messenger (Rasul) and a Prophet (Nabi). A Rasul is that Messenger, who is given a new Shariat (Divine Law) and a new Holy Book. All the Messengers are also known as Prophets, whether or not they are given a new Shariat (Divine Law). Thus a Prophet (Nabi) may be following the previous Shariat and the Holy Book.