Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Or lest you should say) and so that you will not say on the Day of Judgement: (If the Scripture had been revealed unto us) as it was revealed to the Jews and Christians, (we surely had been better guided than are they) we would be swifter in answering the Messenger and we would also have a sounder religion. (Now hath there come unto you a clear proof) a clarification (from your Lord) i.e. the Qur'an and the Messenger, (a guidance) from error (and a mercy) for the one who believes in him; (and who doeth greater wrong) who is more insolent and more daring vis-à-vis Allah (than he who denieth the revelations of Allah) who denies Muhammad (pbuh) and the Qur'an, (and turneth away from them? We award unto those who turn away from Our revelations) Muhammad (pbuh) and the Qur'an (an evil doom) a severe torment (because of their aversion) vis-à-vis Muhammad and the Qur'an.
Or lest you should say, ‘If the Scripture had been revealed to us, we would have surely been more rightly guided than they are’, because of the excellence of our minds. Now indeed a clear proof, a [clear] statement, has come to you from your Lord, and a guidance and a mercy, for him who follows it; and who, that is, none, does greater evil than he who denies God’s signs and turns away from them? We shall surely requite those who turn away from Our signs with dreadful, the most severe, chastisement for their aversion.
Or lest you should say, 'If the Scripture had been revealed to us, we would have surely been more rightly guided than they are', because of the potency of our preparednesses and the purity of our minds, were you to be telling the truth. Now indeed a clear proof has come to you from your Lord, illustrating the modality of how you should wayfare, and a guidance, to your goal, and a mercy, by easing for you the path and its facilitating for you [the way] to the noblest of perfections.
(Otherwise, they would have suffered a calamity because of what their hands sent forth, and said: "Our Lord! Why did You not send us a Messenger We would then have followed Your Ayat.'')28:47.'' The Ayah,
عَلَى طَآئِفَتَيْنِ مِن قَبْلِنَا
(to two sects before us) refers to the Jews and Christians, according to `Ali bin Abi Talhah who narrated it from Ibn `Abbas. Similar was reported from Mujahid, As-Suddi, Qatadah and several others. Allah's statement,
وَإِن كُنَّا عَن دِرَاسَتِهِمْ لَغَـفِلِينَ
("...and for our part, we were in fact unaware of what they studied.") meaning: `we did not understand what they said because the revelation was not in our tongue. We, indeed, were busy and unaware of their message,' so they said. Allah said next,
(Or lest you should say: "If only the Book had been sent down to us, we would surely, have been better guided than they.") meaning: We also refuted this excuse, had you used it, lest you say, "If a Book was revealed to us, just as they received a Book, we would have been better guided than they are.'' Allah also said.
(So now has come unto you a clear proof from your Lord, and a guidance and a mercy.) Allah says, there has come to you from Allah a Glorious Qur'an revealed to Muhammad, the Arab Prophet. In it is the explanation of the lawful and unlawful matters, guidance for the hearts and mercy from Allah to His servants who follow and implement it. Allah said;
(Who then does more wrong than one who rejects the Ayat of Allah and Sadafa away therefrom) This refers to the one who neither benefited from what the Messenger brought, nor followed what he was sent with by abandoning all other ways. Rather, he Sadafa from following the Ayat of Allah, meaning, he discouraged and hindered people from following it. This is the explanation of As-Suddi for Sadafa, while Ibn `Abbas, Mujahid and Qatadah said that Sadafa means, he turned away from it.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, to the Jews and the Christians.
Here "Ayat" are Allah's Revelations presented in the Holy Qur'an as well as His Messenger's noble character and the pure lives of the Believers which clearly distinguished them from the unbelievers, and also those wonderful phenomena of Nature which the Qur'an was putting forward as proofs of the truth of its Message.
"Manifest Signs" are the signs of the Day of Resurrection or some imminent scourge or some other Sign that tray unveil the Reality in such a way as to leave no doubt about it and after which no more chance for test and trial might be left.
That is, if after seeing these "Manifest Signs" a disbeliever repents of his disbelief and professes faith, such a conversion shall be meaningless; likewise the one who professes to believe but adopts the way of disobedience, shall be deemed to have no faith at all, because Faith and Obedience can have any value only up to the time that the reality remains hidden behind the curtain, and the prospect of a long life is ahead and the world with all its allurements is deluding one into believing that there is no Allah and no Hereafter; therefore, one should "Eat, drink and be merry."