It is true of the nine books and its appendices In the name of of Allah the Merciful Praise be to God, Lord of the worlds, and I bear witness that there is no god but God alone with no partner, and I bear witness that Muhammad is the Messenger of God, may God bless him and grant him peace. This is a book in which its authors compiled the hadiths of nine books from the Prophet’s Sunnah and the appendices of the Hadith books, in which they collected hadiths:  Sahih Al-Bukhari  It is true Muslim