Sunni Muslims consider the Sahih al-Bukhari and Sahih Muslim, the collection of hadiths made by Al Bukhari and Muslim ibn Hajjaj, to be the most authoritative hadith collections. Al Bukhari is said to have spent over 16 years gathering over 1,600,000 hadiths and finding the best 7,397 of them. Most of these traditions deal with the life of Muhammad. For Shiites, the words and deeds of their Imams, the progeny of Muhammad, are given that authority. Originally transmitted from generation to generation orally before being compiled, some of these sayings, according to their chain of transmission, are sayings of Muhammad.