The coherence in this sūrahis like a multifaceted gem. It can be studied in many distinct aspects. I shall take upon explaining all the facets of coherence in the sūrah one by one.
The Frist Aspect:
The first aspect of coherence in this sūrah stems from its status as the preface to the Qur’ān and the fact that it, in a concise manner, covers all fundamental themes of the Book (the unicity of God, the sharā’i‘ (laws) and the Last Judgment). It is in consideration of the fact that the sūrah covers the primary themes of the Book the scholars have called it al-mūfiyah (the complementing one). On top of being a preface to the Qur’ān, housing all the fundamental themes of the Book, it is a miniature Qur’ān. This is because a preface to a book is an independent and complete discussion, and yet is always included as an addition to the book. This, however, is in only one aspect. A preface, in another aspect, is part of the book it inaugurates.
That the sūrah is an independent miniature Qur’ān in itself has been gleaned upon by the authorities in the Qur’ān tafsīr. They base this conclusion on their interpretation of the following verse which stresses God’s extraordinary benevolence on the Prophet (sws): “We have given you seven oft-repeated ones and the great Qur’ān (sab‘an min al-mathānī wa al-Qur’ān al-‘azīm).”(15:87)
The scholars, from the earliest times to this day hold that the words sab‘an min al-mathānī(the seven oft-repeated ones) refer to Sūrah al-Fātiḥah. Notice how the Almighty specially calls it the great Qur’ān. This means that this sūrahhas an independent status. If someone holds that the wāw of ‘aṭaf(particle wāw meaning “and” in the verse) is not used to connote gloss and therefore, the most plausible implication is “we have given you these seven verses, and in addition to it, the great Qur’ān” then again, as per this interpretation too, this sūrah is considered a chapter in addition to the Qur’ān. Thus, whatever interpretation of the particle wāw we opt for, the sūrah can be proved to be an independent comprehensive entity. It is based on this that we can understand why the sūrah was not written in the codex of ‘Abdullāh ibn Mas‘ūd (rta), for the Qur’ān was to be written on the hearts of the believers. Gabriel brought the Qur’ān to the Prophet (sws) who then taught it to the Companions (rta). They learnt it from him as an oral word. That is why they themselves had to record it on pages in the form of a book. Thus if it is correct that ‘Abdullāh ibn Mas‘ūd (rta) did not inscribe it in his codex, it is because he considered the fact that the sūrah was written in the heart of every believer. They recite it everyday more than thirty-two times. Whatever is frequently uttered by the tongue of a person does not need to be recorded in written form. It is there in the physical body and the spirit of the person. No despot can snatch it from him. He does not need to write it on a material which needs to be moved and carried separately while at home or on a journey vulnerable to theft and loss.
The Arabs would therefore not put to writing what they could remember and repeat orally. The Qur’ān too has been preserved and secured in this very manner. There are uncountable number of ḥuffāẓ (memorizers) of the holy Qur’ān in the ummah. God has always increased the number of ḥuffāẓ in the ummah.
A similar case is found with the Torah as well. The nation of Israel was required to memorize and secure the statement of the unicity of God in every possible manner. The rest of the Book was given to them in written form. This later part was forgotten and lost. Similarly the Almighty Allah made this sūrah a part of the prayer and decreed that all the believers should write it on their hearts. This is what ‘Abdullāh ibn Mas‘ūd (rta) had in mind when he did not write it in his personal codex. Generally people did not understand his view. They believed he did not consider it part of the Qur’ān. He is quit of the charge of doing so with such evil intention.