The collection of Forty Hadith compiled by al-Imām Yaḥya bin Sharaf an-Nawawi (which actually contains 42 hadiths) has been widely studied in traditional Arabic circles of learning and continues to be one of the basic subjects taught in Islamic courses throughout the world today.
This is primarily due to:
1) the soundness of the collection as a whole – most of its narrations having been taken from the two "Ṣaḥeeḥs" of al-Bukhāri and Muslim,
2) the conciseness and comprehensiveness of the prophetic statements contained therein, and
3) the fact that from them are derived many of the basic principles of `aqeedah and sharī`ah.
Download Compilation of 40 Hadith Al-imam An-Nawawi Pdf