The following is a well known hadith collection by the famous Sunni scholar known as Imam Abu Zakariyya Yahya al-Nawawi (d. 676 AH). He was a prolific scholar who excelled in promulgating the Shafi’i school of Islamic jurisprudence (Madhhab) and his Aqida (creed) was in line with the Sunni school of doctrine known as the Ash’ari school. Many scholars have not only transmitted the contents of this short hadith collection with their own chains of transmission (asnaid) going back to al-Nawawi, but also written detailed commentaries on it in Arabic and other languages.
The above image in the slideshow bar is from an original handwritten manuscript of the Arba’in of Imam al-Nawawi.
Here follows a short biography on this leading Imam of his age:
Biography of Imam al-Nawawi:
Source: Reliance of the Traveller (p. 1086, edited by Sh. N. Keller)