Hadith or ahadith (plural) are sayings and traditions of the Prophet of Islam Muhammed (pbuh).
Hadith contains daily practices of the Prophet (pbuh) these have been passed down via chains of narrators. Ahadith were collected by famous Muhaddiths such as Imam Bukhari and Imam Muslim in their Sahih collections. They verified narrators via very stringent rules, i.e. if a narrator who is known to be unreliable then it would not be taken from that person. It is recorded that Imam Bukhari travelled miles upon miles to hear hadith which he could collect for his collection, he collected over 100,000 ahadith of which only over 7000 can be found in his Sahih collection.