The Ahadith fall into two categories, "Hadith Qudsi (sacred hadith) in which Allah (God) himself is speaking in, as it were, a complementary revelation through the prophet, and Hadith Sharif (noble hadith), the prophet's own acts and utterances." [The Concise Encyclopedia of Islam, Harper & Row, Publishers, Inc. San Francisco, 1989, page 141.]

The most famous and universally accepted among the six collections of Hadith are those of Sahih Bukhari and Sahih Muslim.