The individual letters in the beginning of some Surahs are among those things whose knowledge Allah has kept only for Himself. This was reported from Abu Bakr, `Umar, `Uthman, `Ali and Ibn Mas`ud. It was said that these letters are the names of some of the Surahs. It was also said that they are the beginnings that Allah chose to start the Surahs of the Qur'an with. Khasif stated that Mujahid said, "The beginnings of the Surahs, such as Qaf, Sad, Ta Sin Mim and Alif Lam Ra, are just some letters of the alphabet.'' Some linguists also stated that they are letters of the alphabet and that Allah simply did not cite the entire alphabet of twenty-eight letters. For instance, they said, one might say, "My son recites Alif, Ba, Ta, Tha... '' he means the entire alphabet although he stops before mentioning the rest of it. This opinion was mentioned by Ibn Jarir.