Imam al-Nawawi’s collection of 40 Hadiths is one of the most important collections of hadiths we have today. Imam al Nawawi actually compiled a total of 42 hadiths for this collection, not 40. He was one of the greatest scholars of Islam and lived from 631 A.H. to 676 A.H, passing away at the age of 45. Allah (swt) granted him blessing and success in his work so that he could make great contributions to Islam before passing away at a relatively young age.
Imam al-Nawawi was a scholar in many different disciplines of Islamic studies. The vastness of his works in these different areas is so great that if an individual decides to study fiqh, hadith, spirituality, or Quran; one would need to pass through Imam al- Nawawi. Along with the 40 Hadiths, he authored Riyad al-Saliheen, Al-Adhkar, and commentary of Sahih Muslim and Sahih Bukhari.
Imam al-Nawawi was one of the foremost figures of the Shafi’ madhab and the largest and most substantial book he wrote in this regard is called Al Majmua’ which is about 30 volumes. It is a work of comparative fiqh because he brings all of the opinions of different madhab’s on different issues together.