The following excerpt is taken from “The Message of the Quran” pg. 1250-1252:
About one-quarter of the Qur’anic surahs are preceded by mysterious letter-symbols called muqatta’at (“disjointed letters”) or, occasionally, fawatih (“openings”) because they appear at the beginning of the relevant surahs. Out of the twenty-eight letters of the Arabic alphabet, exactly one-half that is, fourteen – occur in this position, either singly or in varying combinations of two, three, four or five letters. They are always pronounced singly, by their designations and not as mere sounds – thus: alif lam mim, or ha mim, etc.
The significance of these letter-symbols has perplexed the commentators from the earliest times. There is no evidence of the Prophet’s having ever referred to them in any of his recorded utterances, nor of any of his Companions having ever asked him for an explanation. None the less, it is established beyond any possibility of doubt that all the Companions obviously following the example of the Prophet – regarded the muqatta’at as integral parts of the surahs to which they are prefixed, and used to recite them accordingly: a fact which disposes effectively of the suggestion advanced by some Western orientalists that these letters may be no more than the initials of the scribes who wrote down the individual revelations at the Prophet’s dictation, or of the Companions who recorded them at the time of the final codification of the Qur’an during the reign of the first three Caliphs.
Some of the Companions as well as some of their immediate successors and later Qur’an commentators were convinced that these letters are abbreviations of certain words or even phrases relating to God and His attributes, and tried to “reconstruct” them with much ingenuity: but since the possible combinations are practically unlimited, all such interpretations are highly arbitrary and, therefore, devoid of any real usefulness. Others have tried to link the muqatta’at to the numerological values of the letters of the Arabic alphabet, and have “derived” by this means all manner of esoteric indications and prophecies.
Yet another, perhaps more plausible interpretation, based on two sets of facts, has been advanced by some of the most outstanding Islamic scholars throughout the centuries:
Firstly, all words of the Arabic language, without any exception, are composed of either one letter or a combination of two, three, four or five letters, and never more than five: and, as already mentioned, these are the forms in which the muqatta’at appear.
Secondly, all surahs prefixed by these letter-symbols open, directly or obliquely, with a reference to revelation, either in its generic sense or its specific manifestation, the Qur’an. At first glance it might appear that three surahs (29, 30 and 68) are exceptions to this rule; but this assumption is misleading. In the opening verse of surah 29 (Al-‘Ankabut), a reference to revelation is obviously implied in the saying, “We have attained to faith” (amanna), i.e., in God and His messages. In surah 30 (Ar-Ram), divine revelation is unmistakably stressed in the prediction of Byzantine victory in verses 2-4. In verse 1 of surah 68 (Al-Qalam) the phenomenon of revelation is clearly referred to in the evocative mention of “the pen” (see note 2 on the first verse of that surah). Thus, there are no “exceptions” in the surahs prefixed by one or more of the muqatta’at: each of them opens with a reference to divine revelation.
This, taken together with the fact that the muqatta’at mirror, as it were, all word-forms of the Arabic language, has led scholars and thinkers like Al-Mubarrad, Ibn Hazm, Zamakhshari, Razi, Baydawi, Ibn Taymiyyah, Ibn Kathir to mention only a few of them – to the conclusion that the muqatta’at are meant to illustrate the inimitable, wondrous nature of Qur’anic revelation, which, though originating in a realm beyond the reach of human perception (alghayb), can be and is conveyed to man by means of the very sounds (represented by letters) of ordinary human speech.
However, even this very attractive interpretation is not entirely satisfactory inasmuch as there are many surahs which open with an exphcit reference to divine revelation and are nevertheless not preceded by any letter-symbol. Secondly – and this is the most weighty objection – the above explanation, too, is based on no more than conjecture: and so, in the last resort, we must content ourselves with the finding that a solution of this problem still remains beyond our grasp. This was apparently the view of the four Right-Guided Caliphs, summarized in these words of Abu Bakr: “In every divine writ (kitab) there is [an clement of] mystery – and the mystery of the Qur’an is [indicated] in the openings of [some of] the surahs.”
Asad, Muhammad (1980). (pg. 1250-1252). The Message of the Quran. http://www.islamicweblibrary.com/wp-content/uploads/2020/04/55877864-54484011-Message-of-Quran-Muhammad-Asad-Islam-Translation.pdf