The meaning of al-huroof al-muqatta’ah in the Qur’aan

A group of scholars, such as the Rightly-Guided Khaleefahs (may Allaah be pleased with them), and others among the Sahaabah, Taabi’een and their followers, refrained from interpreting this aayah and others which contain al-huroof al-muqatta’ah [letters which appear at the beginning of some soorahs]. It was not narrated that the Prophet (peace and blessings of Allaah be upon him) interpreted them, so it is preferable for us to say Allaah knows best what they mean. But it was narrated that some of the mufassireen among the Sahaabah, Taabi’een and their followers did interpret them, and they differed as to their interpretation. 

Al-Saheeh al-Masboor min al-Tafseer bi’l-Ma’thoor by Dr Hikmat Basheer, vol 1, p. 94 

Some of the scholars tried to discover the wisdom behind these letters and said: These letters are mentioned – and Allaah knows best – at the beginning of soorahs which point to the miraculous nature of the Qur’aan, which implies that all mankind is unable to match it, even though it is composed of the letters that they use in their daily speech. This was the view supported by Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) and was approved of by Abu’l-Hajjaaj al-Mazzi (may Allaah have mercy on him). And Allaah is the Source of strength. May Allaah bless our Prophet Muhammad and his family and companions, and grant them peace. 

Fataawa al-Lajnah al-Daa’imah, vol. 4, p. 144.