Besides Bukhari, Sahih Muslim is considered to be the most authentic book of Hadith. Between Sahih Bukhari and Sahih Muslim, there are around 2000 Hadith which are common in both the collection and any hadith found in both the books is considered to be Saheehayn.
Imam Muslim was born in Naysabur (Nishapur, that is present day Iran) in Hijri 206. But He was attributed to the Kushayri Arab Tribe. He had travelled the entire Arab Peninsula before in quest of knowledge before he settled in Nishapur. At his very early age started seeking knowledge similar to his shaykh (teacher) Imam Bukhari.
He was highly influenced by the comprehension skills and authority over Hadith of Imam Bukhari after he met him, he then joined him as his student. He compiled Sahih Muslim as a response to questions from one of his students. He had a collection of 300 thousand Hadith from which he selected around 4000 for his Sahih Muslim. He has recorded only those hadith which, at least, two reliable tabi’een (successors of sahaba) had heard from two sahaba and he stuck to this principle throughout the subsequent chain of narrators.
Abu Isa Tirmidhi, Ibn Khuzaimā and Ad Dhahābi were his three extremely popular students. He stood by Imam Bukhari, during the infamous political controversy that met Imam Bukhari during his visit in Nishapur during his last years of life. When Yahya ibn Yahya al-Nishaburi al-Tamimi, announced in his gathering, that who ever considered Imam Bukhari to be his teacher should get up and leave his gathering, Imam Muslim got up and left the gathering thus showing his solidarity with his Ustaad, the great Muhaddith Imam Bukhari. When Imam Bukhari left the city, Imam Muslim was the only person present for farewell.
Both of these Muhadditheen put a close observation over the isnaad to maintain its Authenticity from any false propagations and weaknesses.
The popular Sharah (commentary) of Sahih Muslim is by Imam Nawawi- ‘Sharah Sahih Muslim’.
Imam Muslim died at the age of 54 in Hijri 261 and buried in Nasarabad, a suburb of Nishapur.