Sahih Muslim, Urdu translation, Vol 13

After Quran and Sunnah, the third source of guidance is hadeeth. By Hadeeth we mean those traditions which were compiled from the statements of diverse narrators a century and a half after the Holy Prophet. The distinction between sunnah and hadeeth is that sunnah is a continuous practice which was started by the Holy Prophet (pbuh).
When the time of the companions of the Holy Prophet had passed some of their successors thought of compiling the ahadeeth and they were compiled. There is no doubt that most of the compilers of hadeeth were very pious and righteous. They tested the accuracy of ahadeeth as far as it was possible and tried to steer clear of such of them as in their opinion were manufactured, and they rejected every hadeeth any narrator of which was of doubtful veracity. As all this activity was ex post factum, it was no more than conjecture; yet it would be most unfair to say that all ahadeeth are vain and useless and false. So much care was taken in compiling the ahadeeth, and such research and criticism were employed in the task, that they cannot be matched in any other religion.
Sahih Muslim is the collection made by Muslim bin Al-Hajjaj 200 years after passing away of Holy Prophet of Islam. It is considered second most important collection of ahadeeth after Sahih Bukhari