Sunan al-Tirmidhi is a significant collection of hadith, or sayings and actions of the Prophet Muhammad. Compiled by the Islamic scholar Abu 'Isa Muhammad ibn 'Isa al-Tirmidhi in the 9th century, it is one of the six major hadith collections in Sunni Islam. The work is known for its systematic approach, categorizing hadiths based on various topics, such as prayer, fasting, and ethics. The collection includes approximately 3,956 hadiths, many of which are classified by their authenticity. Sunan al-Tirmidhi is particularly valued for its commentary on the reliability of each hadith, making it a crucial resource for scholars and students of Islamic teachings.