The Holy Qur’ān itself testifies that it was not revealed in a single instance, but rather in a piecemeal fashion (25:32):
And those who disbelieve say: “Why is not the Quran revealed to him all at once?” Thus (it is sent down in parts), that We may strengthen your heart thereby. And We have revealed it to you gradually, in stages
Parts of the Holy Qur’ān were revealed considering the circumstances of its addressees. Therefore, when some of the directives were relaxed in some aspect or some others were complemented by new revelations, the new addition was put next to the original command. Sometimes these later revelations were placed at the end of the discussions they complemented. Since the shifts in the discourse have been marked by the rukū‘ division, people find it difficult to understand the interrelation of such complementary passages with the preceding discussions. We can study this interrelation between the two by the help of the following facts.
God Himself has explained that such verses are explanatory verses, revealed in accordance with His promise to the Prophet (sws) that He would explain whatever called for an explanation and would arrange it in a set order when He says (75:8-9):
When We have recited it to you follow that recitation of Ours and then We shall Ourself explain it
It is in accordance with this promise that whenever a complementary verse or verses were revealed it was pointed out that these verses are explanatory verses. Also, these complementary verses have been expressed in a different style: they do not follow the pattern of the verses that follow and precede them. This also serves as an indication to the fact that they are explanatory verses.
Some of the explanatory verses are betrayed in their style by the fact that they respond to an implicit question. Many such verses clearly indicate that they are pointing out towards a finer point within the discourse.
It needs to be appreciated that some Sūrahs have been transmitted via the tongue of the Prophet (sws) and some via the tongue of the Archangel Gabriel and many more by the Almighty himself. This is in agreement with the style found in the discourse of the earlier revealed Books . The Holy Qur’ān has clearly explained this fact (42:51):
It is not possible for any mortal that God should speak to him (face to face) except (that He does so) by revelation, or from behind a veil, or through a messenger sent and authorized by Him to make known His will
At another place God Almighty says (2:97):
Say, “Whoever is an enemy to Gabriel (must know) that he [Gabriel] has revealed it to your heart by God’s command.”
Yet at another place the same has been put thus (81:19-25):
This is a word of a gracious and mighty messenger, held in honor by the Lord of the Throne, obeyed in heavens, faithful to his trust. No, your compatriot is not mad. He saw him on the clear horizon. He does not grudge the secrets of the unseen; nor is it the utterance of an accursed devil
Still at another place the Almighty says (69:40-43):
This is indeed the utterance of a noble messenger. It is no poet’s speech: you seldom believe! It is no soothsayer’s divinations: how little you reflect! It is a revelation from the Lord of the universe.
This issue has been extensively discussed in my book ’Asālīb al-Qur’ān (Styles of the Qur’ān).
The above discussion, it is hoped, has made it clear that the Holy Qur’ān contains verses which have been incorporated later as required explanations or as complements to some earlier discussions. Many verses have been transmitted via the tongue of Gabriel; many others issue from the Prophet (sws). A major portion, however, is the direct speech of God. In order to understand the Holy Qur’ān and interpret it you have to make out which verse issues from whom and who it is addressing. Without successfully identifying the addressors and the addressees you will not be able to understand the coherence in the text. This can be explained through an example. In an allegorical story many characters are made to talk according to their role in the plot. If someone assumes that all these things have been told by a single character he will certainly fail to make out any connection between the parts of the whole story.
This example I have offered only in order to explain my point fully. The word of God, indeed, does not suffer from such limitations: His word is exalted and does not stand in need for such examples and analogies.