The six major collections are Sahih al-Bukhari, Sahih Muslim, Sunan Abu Dawud, Jami at-Tirmidhi, Sunan an-Nasa'i and Sunan Ibn Majah. Hadith are classified as sahih (sound), hasan (good), da'if (weak) and mawdu' (fabricated). Selected hadith teach unity, avoiding ill motives such as suspicion and envy, and caring for one another like one body.