History of Hadith,
First book of Hadith was collected by Bukhari, Sunnies call it Sahih (truthful, correct) Bukhari. Bukhari lived about 3041 Kilometers from Mecca, about 200 years after prophet. Collection of quotes from mostly illiterate people. Shiaa’s objection is that it’s 7563 stories contains only 29 hadith that names their leader, Imam Ali, the third Khalifa, prophet’s son in law, which only 8 of the 29 hadith are in his approval or praise, while his teacher Ahmad Ebn Hanbal had more than 200 pages in admiring him.
In his book, he names all people who had been involved & quoted each other in a chain, all verbal, sometimes eight to ten generations away from the original quote.
A new generation of historians, Hadith writers, specialists in knowing the honesty of people who lived first two hunderd years, and within ten generation, (Science of Rejal علم رجال) on people who lived long time before them, and another Science, as they call it, in learning the logical flow of hearsay vs. Quran (علم درایه) , after Bukhari spent all their time and effort finding correct hadith in contradicting each other , finding opposite quotes from past generations, disputing each other’s honesty and trustworthiness.
Islam and Quran started an organized religion, specialists of hearsay, unprecedented until then, still main source of division.
Why is this issue any important at all?
All the sectarian and political violence, killings of adulterers, homosexuals or converts are not in Quran, but are in Hadiths.
Despite the Muslims shortcomings, Quran’s promised salvation does not depend on believing any particular prophet. Equates their guidance as being from one source, the same source, forbids of any of them and most important, it stands for freedom to choose. Hadith does not!