It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) concerning the sayings of Allah Almighty: "Alif Lam Mim. That is the Book" [Surah al-Baqarah: 1-2] , that he said: "Alif Lam Mim" is a letter of the name of Allah, and "the Book" means the Qur'an, while "There is no doubt in it" means that there is no room for any kind of doubt or suspicion in it (the Divine Word). This hadith is sahih (authentic) on the condition of Muslim, but the two Shaykhs (Imam Bukhari and Muslim) did not record it.