Therefore his followers are Sunnat Issa Muslims. Those who say there is no such thing as that are denying all the prophets because the followers of Abraham were followers of his sunnah and the followers of Musa were followers of his sunnah and just like people abandoned those ways but kept the name so do the followers of the prophet Muhammad.
There is only one difference with Muhammad's sunnah in that it centers around the revelation of a book for all the monotheists and preserves many of the stories of the time that he lived. It doesn't cancel any of the other sunnahs or any of the other books, it is just produced differently and has a different nature.
A lot of people who have been compelled to be Sunnat Muhammad against their natures and inclinations are proud of saying things like there is no sunnat Issa and that they know things Allah hasn't revealed to them. This is no different than what happened in any of the other sunnahs.
When the Quran was brought to my Dad he and others around him easily recognized that it was from the same source as the teachings they were on. They also realized it was not aimed specifically at them, and when they read it they saw clearly that "the people of the fitra" were specifically mentioned as being of Allah but not under Shariah. They understood that Allah sent this book to provide government for people who continued to insist on having one, and that if pretty well defined who those people would always be, but it changed nothing concerning them, though it was a good read
*speaking of kings and queens, we do have those but its not some unrelated person bossing us around, our kings are the fathers and our queens are the mothers but the people who come to help with the kids also call them king and queen though it translate closer to Dad and Mom, and as families grow larger we fill space and just like anywhere there are older brothers and sisters and more and less responsible people, and all around the edges of various definitions are the people who aren't sure our system is for them and they try other ways and sometimes they find out they don't like other people's ways and sometimes they do and from time to time we have to tell people they don't represent us anymore*
