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The sayings of the prophet Muhammad (p.b.u.h) were not put down to writing, immediately after his death. This incident resulted in the appearance of some non-authentic sayings
attributed to him.
In order to distinguish the authentic traditions from those which are not authentic, Islamic specialists devided them into different categories as - musnad; mursal; maruf and munkar; mardud and matruk; muttafig and muftariq; mutalif and mukhtalif, etc. .
Another approach in this direction was some kind of research into the personality and qualifications of the narrators of Hadith,
an approach which was named Elmurrijal.
The later approach may be considered the best way for
distinguishing the correct Hadith from non correct one.