Saheeh Al-Bukhaari:

Of all the works of Hadeeth, Saheeh Al-Bukhaari and Saheeh Muslim are regarded as the most authentic and authoritative books, after Al-Quran. Indeed the very word "Saheeh" means "authentic". Saheeh Al-Bukhaari was compiled by Imaam (leader) of Hadeeth, Mohammad Ibn Ismaa'eel Al-Bukhaari, born 194H in Bukhaara, central Asia. He traveled at an early age seeking knowledge to Hijaaz (Makkaah and Madeenah), Ancient Syria, Iraq Egypt etc. He  devoted more than 16 years of his life to the actual compilation of this work. He  learnt from more than 1000 scholars. It is said that Imaam Al-Bukhaari  collected over 300,000 Hadeeths and he himself memorized 200,000 of which some were unreliable. He  wrote many books especially on the bibliography of Hadeeth narrators and other books on various issues of Fiqh (Islamic jurisprudence). However, his book 'Saheeh Al-Bukhaari', stands out for being the most authentic book of Hadeeth. It was also the first book to contain only authentic Hadeeths, while previous books contained authentic and non-authentic Hadeeths, as well as sayings of the companions  and others. Imaam Al-Bukhaari  died in his hometown, Bukhaara in the territory of Khurasaan (West Turkistan), in the year 256H.

He  grouped the traditions of the Prophet  under various headings dealing with specific points of Islamic jurisprudence. In his time, the schools of law had been generally established and his objective was to catalogue the traditions he regarded as authentic in relation to their respective topics of jurisprudence.

Before he recorded each Hadeeth, he  would perform ablution and offer a two-Rak'ah prayer and supplicate to Allaah. Many religious scholars of Islam tried to find fault in the great remarkable collection, but without success. It is for this reason, they unanimously agreed that the most authentic book after the Book of Allaah is Saheeh Al-Bukhaari.

Some facts about Saheeh Al-Bukhaari:

1. It contains 7,275 Hadeeths, which he  chose from the large number of Hadeeths that he  had collected.
2. The number of complete unrepeated Hadeeths is 2230.
3. All the Hadeeths mentioned are authentic.
4. The conditions for accepting a Hadeeth were very stringent. Such as:

a) The chain of narrators must be linked, i.e. every narrator must have met his predecessor, (the man of whom he heard the Hadeeth from, up to the Prophet .)

b) For it to be enclosed in the Saheeh, the narrators must be of the highest caliber regarding their piety, manners, memory, integrity, etc.

5. The book is not a mere book of narrations; it is essentially a course of study on Hadeeth, its derivatives, inductions and research.

6. Each one of its 97 chapters is headed by a relevant verse from the Quran that complements the meaning of the Hadeeths quoted. 

7. Finally, much more could be said about this monumental work, however, it is enough to say that many people have reached fame and achieved the highest qualifications by studying the book, researching it and commenting on it.

Saheeh Muslim:

Saheeh Muslim is the second most authentic book of Hadeeth after Saheeh Al-Bukhaari, compiled by Imaam Muslim ibn Al-Hajaaj Al-Nisapuri . Born in 202H and died in 261 H. He  traveled widely to gather his collection of Hadeeth to Iraq Hijaaz, Ancient Syria, and Egypt. He learnt from many scholars, most of which were Al-Bukhaari's teachers. He also learnt from the Imaam Al-Bukhaari himself  and became his most loyal student. Like Imaam Al-Bukhaari, Allaah have mercy upon him, he, Allaah have mercy upon him, wrote many books on the sciences of Hadeeth.

He, Allaah have mercy upon him, sought not so much to complement the issues at stake in the fiqh, the lslamic jurisprudence, but rather to produce a collection of sound traditions, an authentic record, on which future studies of Hadeeth could be based.

Some facts about Saheeh Muslim:

1. The book contains 4000 non-repeated Hadeeths and 12000 repeated ones.
2. Many narrations are mentioned in Saheeh Al-Bukhaari, but with different chain of narrators.
3. In every chapter more than one Hadeeth with the same meaning but with different chains and text are listed. The first Hadeeth in each chapter is the strongest, followed by weaker narrations in order to strengthen weaker narrations.
4. Excellent classification.
5. The book is forwarded by a detailed introduction about the basis of the sciences of Hadeeth.

Saheeh Al-Bukhaari is preferred over Saheeh Muslim based on the authenticity of the Hadeeths. Imaam Al-Bukhaari  was more strict in selecting Hadeeths (chains) than Imaam Muslim . Besides considering all the conditions of a Saheeh Hadeeth, Imaam Al-Bukhaari  stipulated a further condition that a narrator should meet the person from whom he is narrating the Hadeeth.

Imaam Muslim  however, did not stipulate the evidence of meeting the narrator from whom he is narrating, but according to him, it is sufficient to accept the Hadeeth of a narrator if he lives in the same period and there was the possibility of meeting the narrator from whom he is reporting the Hadeeth. So, the condition of Imaam Muslim  was less strict than the condition of Imaam Al-Bukhaari .  

While Bukhaari's compilation is considered the more reliable of the two, Muslim's arrangement of his material has been recognised as superior, and rightly so. While Al-Bukhaari  made the traditions in his collection testify to his own schedule of various points of law, Muslim  left them to speak for themselves.