There are different types of Haddis and the best type of Haddis are called Sahih haddis
For Haddis to fall under the Sahih it should fulfil 5
conditions and those five conditions are as below:
1. Complete Chain of
narrators. There should be a complete chain of narrators .and you should be
able to verify according to history that these narrators have met each other so
first condition is (continuous chain
connecting back to PBUH)
2. Narrator in that chain till collection all narrators
should deem to be trustworthy and reliable is call al-adal (some one richest) any
narrator with in the chain should have not done anything shameful even it is
not harram
3. Narrator should have precision and have extra
ordinary memory
4. Narration should not be contradicting with any existing
sahih Haddis that is more trust worthy
5. Fifth and and most important that haddis should be free from and hidden defects.
What are hidden defects
You might have come across a lot of haddis narrated by Hashim and his haddis are sahih Haddis and he was a trust worthy narrator, however one incident that occured and induced a hidden defect according to Imam bukhari , and Muslim.
Despite of hidden defects Imam al hakim put haddis from Hashim in a book called al mustadrak al hakim but mind that they are not Sahih Haddis.
Hashim learnt some haddis from his teacher imanam Muhmmad Ibn Shihab al-Zuhri Died AH 124 (741/742 AD) he noted those haddis on paper or some stuff used at that time. One day Hashim borrowed his
haddis noted to his friend and due to
heavy wind Haddis notes flew and he lost them, but Hashim still quoted the haddis from his memory and that got suspecious and this
is called ailla. This is one form of hidden defect which didnt fullfil all the requirement of Sahih Haddis.
So Imam Bukhari didnt took any haddis that Hashim narrated from Imam Muhammad ibn Shihab al Zihari. However his other haddis are considered without any minor defects.
If Narrator has not got exceptional memory but have got good
memory that type of haddis is call Hassan haddis
