Part of Believing in the Prophet is to Believe:
lThat he is the intermediary between Allah and His creation with regards to conveying His command and prohibition, promise and threat and what He declared to be lawful and prohibited.
lThe lawful is what Allah and His Messenger declared to be lawful, the prohibited is what Allah and His Messenger declared to be prohibited
lThe religion comprises only that which Allah and His Messenger (SAW) legislated.