Specialized biographical studies called Ilm ar-Rijal were made to determine how trustworthy each narrator was and, using that information, how authentic each hadith was.

Its goal is to distinguish authentic hadith from hadith unacceptable in establishing sanctioned religious knowledge or practice.

However, the authenticity of this story has been questioned by Islamic scholars as no such story appears in the authentic hadith.

There are also other collections of hadith which also contain many authentic hadith and are frequently used by scholars and specialists.

He intended to include only authentic hadith a goal which, to a large extent, he accomplished.

It has the distinction of being one of small number of collections intended by the respective authors to contain only authentic hadith.

According to Ibn Hajar, if a narration which goes against another authentic hadith is reported by a weak narrator, it is known as munkar.

It is a 20-volume collection, meant to include all 'authentic' Hadith from the available Shia hadith books, checking their authenticity on the strict principles of Ilm-ur-Rajjal.

In addition, al-Dhahabi said, "Bukhari was heard saying, 'I have memorized one hundred thousand authentic hadith and two hundred thousand which are less than authentic.'"

Another authentic Hadith says that Muhammed said :