There is Quran-Which we belive as infalliable and keep that as a benchmark to verify any event in Prophet Muhammed history Then there is Hadith - which are narrations of people who saw things as happened.There are several hundred thousands of them and there are many fabrications as they are just narrations by human beings.Muslims have a very sophicated technique and apply many consistent characteristics to filter these things out. 1.If it violated with Quran -It is a fabriation 2.If there are many contradictaing events -this is a fabrication 3.If the narrator is found be unreliable and lying-This is deemed to be fabrication 4.Analaysis of text and pattern (which gave birth to crptoanalysis )and if it deviates then it is a fabrication
The last source is biographies - They are not hadiths-There are hundreds of them.The so called biographers like Tabari have writen their version of history 400 years after the death of Prophet Muhammed.We are talking about a age when there is no concept of printing.
There are many biographies and Muslims take the incidents as true only when all the major narrations corroborate with each other.
Some how islamic critics take anything that has a arabic name as a legitimate source and ask muslims to belive in it.which is wrong.
