Imam Muslim (Muslim ibn al-Hajjaj) was born in 202AH (817/818CE) and died in 261AH (874/875CE). He traveled widely to gather his collection of ahadith (plural of hadith), including to Iraq, Saudi Arabia, Syria and Egypt. Out of 300,000 hadith which he evaluated, approximately 4,000 were extracted for inclusion into his collection based on stringent acceptance criteria. Each report in his collection was checked for compatibility with the Qur'an, and the veracity of the chain of reporters had to be painstakingly established. Sunni Muslims consider it the second most authentic hadith collection, after the Sahih Bukhari.

However it is important to realize that Imam Muslim never claimed to collect all authentic traditions. He tried to collect only traditions that all Muslims should agree on about accuracy. There are other scholars who worked as Muslim did and collected other authentic reports.

According to Munziri, there are a total of 2200 hadiths (with no repetition) in Sahih Muslim. This would bring the total of Sahih Bukhari and Sahih Muslim to 3000 ahadith. According to most Hadith scholars, there are 1400 authentic hadiths that are reported in other books (mainly the Six major Hadith collections).