Hadith is an important extension of the Muslim faith. Hadith are stories about the prophet Muhammad (PBUH), verified by his companions. When reading hadith you will often find the same story repeated several times, this generally means that more than one companion of the prophet has shared and verified the same story. The biggest and most authentic hadith books are that of Sahih Bukhari & Sahih Muslim.
Say, "Obey Allah and the Messenger." But if they turn away - then indeed, Allah does not like the disbelievers. Surah (3) Aya (32)