Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Verily We have brought them a Scripture) Allah says: We have sent them Muhammad (pbuh) with the Qur'an (which We expound with knowledge) with knowledge from Us; it is also said that this means: We have taught it, (a guidance) from error (and a mercy) from torment (for a people who believe) in Muhammad (pbuh) and the Qur'an.
And indeed We have brought them, that is, the people of Mecca, a Book, the Qur’ān, which We have detailed, [which] We have made clear through tidings and the Promise [of reward] and the Threat [of punishment], with knowledge (‘alā ‘ilmin is a circumstantial qualifier, in other words, ‘knowing what has been detailed in it’), a guidance (hudan is [also] a circumstantial qualifier referring to the hā’ [the suffixed pronoun of fassālnā-hu, ‘which We have detailed’]) and a mercy for a people who believe, in it.
And indeed We have brought them a Book, which We have detailed with knowledge, that is, [We have given them] the human body, which is differentiated into limbs, extremities, organs and senses which can be used to attain perfection in accordance with what is decreed by Divine knowledge. The interpretation of this [verse] is [that it is a reference to] what is fulfilled by His command in the final sequel such as the transformation [of this body] into what cannot be used for that [perfection] at the Gathering in terms of configurations, forms and figures that correspond to their attributes and beliefs commensurate with His statement He will assuredly requite them for their descriptions [Q. 6:139] and where He says And We shall assemble them on the Day of Resurrection on their faces, blind, dumb and deaf [Q. 17:97].
Allah states that He has left no excuse for the idolators, for He has sent to them the Book that the Messenger came with, and which is explained in detail,
كِتَابٌ أُحْكِمَتْ ءايَـتُهُ ثُمَّ فُصِّلَتْ
((This is) a Book, the Ayat whereof are perfected (in every sphere of knowledge), and then explained in detail ) 11:1 Allah said next,
فَصَّلْنَـهُ عَلَى عِلْمٍ
(We have explained in detail with knowledge) meaning, `We have perfect knowledge of what We explained in it'. Allah said in another Ayah,
(He has sent it down with His Knowledge,) 4:166 The meaning here is that after Allah mentioned the loss the idolators end up with in the Hereafter, He stated that He has indeed sent Prophets and revealed Books in this life, thus leaving no excuse for them. Allah also said;
(If you could but see when they will be held over the (Hell) Fire! They will say: "Would that we were but sent back! Then we would not deny the Ayat of our Lord, and we would be of the believers!'' Nay, it has become manifest to them what they had been concealing before. But if they were returned (to the world), they would certainly revert to that which they were forbidden. And indeed they are liars) 6:27-28 Allah said here,
(Verily, they have lost themselves and that which they used to fabricate has gone away from them.) meaning, they destroyed themselves by entering the Fire for eternity,
وَضَلَّ عَنْهُمْ مَّا كَانُواْ يَفْتَرُونَ
(And that which they used to fabricate has gone away from them.) What they used to worship instead of Allah abandoned them and will not intercede on their behalf, aid them or save them from their fate.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, "The Qur'an gives details of the reality and of the correct attitude man should adopt in the life of this world and of the basic principles of the Right Way of life. Then it may also be noted that these details an not based on guess-work or conjecture or whim but on pure and accurate knowledge."
The Qur'an is `Guidance' because its teachings arc so clear that they show the right way to anyone who ponders over them. Moreover, the practical effects of that guidance can be seen in the lives of those who believe in it and follow its teachings. And it is really a great `blessing' because it brings a blessed change in the mental attitude, the moral out-look and the character of the one who accepts it. The truth of this was being proved by the wonderful changes that were taking place in the lives of the Companions of the Holy Prophet.
In other words, it means: The distinction between right and wrong has been made clear in the most rational manner, but there are people who do not see it; they have the examples of those who have been totally changed for the better by following the Right Way, though they were just like them before this, yet they do not learn any lesson from this. Such people will admit their error only when they will suffer the consequences of their wrong ways.
Their case is similar to the case of a patient, who does not follow the advice of the physician, nor does he learn a lesson from the other patients, who regained their health by following the instructions of the physician, when they were suffering from the same disease. Such a patient will admit that the ways of life he was following were fatal but only on his death-bed.
When they will see, with their own eyes, the consequences of the rejection of the Message of the Prophets, they will say, "Now that we have witnessed that reality, which we denied at the time, when the Messengers informed us about it, we will behave in a different way if we are sent back to the same world". For response to such a request, see VI: 27, 28; XIV: 44, 45; XXXII: 12, 13; XXXV: 37; XXXIX: 56-59;XL: 11, 12.