The Disbelievers ask for the Punishment to be delivered now!
Allah said,
وَيَسْتَعْجِلُونَكَ
(They ask you to hasten), in reference to the disbelievers,
بِالسَّيِّئَةِ قَبْلَ الْحَسَنَةِ
(the evil before the good,) meaning, the punishment. Allah said in other Ayat that they said,
وَقَالُواْ يأَيُّهَا الَّذِى نُزِّلَ عَلَيْهِ الذِّكْرُ إِنَّكَ لَمَجْنُونٌ - لَّوْ
مَا تَأْتِينَا بِالْمَلَـئِكَةِ إِن كُنتَ مِنَ الصَّـدِقِينَ - مَا نُنَزِّلُ الْمَلَـئِكَةَ إِلاَّ بِالحَقِّ وَمَا كَانُواْ إِذًا مُّنظَرِينَ
(And they say: "O you to whom the Dhikr (the Qur'an) has been sent down! Verily, you are a mad man! Why do you not bring angels to us if you are of the truthful" We send not the angels down except with the truth (i.e. for torment), and in that case, they (the disbelieves) would have no respite!)15:6-8, and two Ayat;
وَيَسْتَعْجِلُونَكَ بِالْعَذَابِ
(And they ask you to hasten on the torment!)29:53-54 Allah also said,
سَأَلَ سَآئِلٌ بِعَذَابٍ وَاقِعٍ
(A questioner asked concerning a torment about to befall.) 70:1,
يَسْتَعْجِلُ بِهَا الَّذِينَ لاَ يُؤْمِنُونَ بِهَا وَالَّذِينَ ءَامَنُواْ مُشْفِقُونَ مِنْهَا وَيَعْلَمُونَ أَنَّهَا الْحَقُّ
(Those who believe not therein seek to hasten it, while those who believe are fearful of it, and know that it is the very truth.)42:18, and,
وَقَالُواْ رَبَّنَا عَجِّل لَّنَا قِطَّنَا
(They say: "Our Lord! Hasten to us Qittana.)38:16, meaning, our due torment and reckoning. Allah said that they also supplicated,
وَإِذْ قَالُواْ اللَّهُمَّ إِن كَانَ هَـذَا هُوَ الْحَقَّ مِنْ عِندِكَ
(And (remember) when they said: "O Allah! If this (the Qur'an) is indeed the truth from You.)8:32 They were such rebellious, stubborn disbelievers that they asked the Messenger to bring them Allah's torment. Allah replied,
وَقَدْ خَلَتْ مِن قَبْلِهِمُ الْمَثُلَـتُ
(while exemplary punishments have indeed occurred before them.) Meaning, `We have exerted Our punishment on the previous disbelieving nations, and made them a lesson and example for those who might take heed from their destruction.' If it was not for His forbearance and forgiveness, Allah would have indeed punished them sooner. Allah said in another Ayah,
وَلَوْ يُؤَاخِذُ اللَّهُ النَّاسَ بِمَا كَسَبُواْ مَا تَرَكَ عَلَى ظَهْرِهَا مِن دَآبَّةٍ
(And if Allah were to punish men for that which they earned, He would not leave a moving creature on the surface of the earth.)35:45 Allah said in this honorable Ayah,
وَإِنَّ رَبَّكَ لَذُو مَغْفِرَةٍ لِّلنَّاسِ عَلَى ظُلْمِهِمْ
(But verily, your Lord is full of forgiveness for mankind in spite of their wrongdoing.) He is full of forgiveness, pardoning and covering the mistakes of people, in spite of their wrongdoing and the errors committed night and day. Allah next reminds that His punishment is severe, so that fear and hope are both addressed and mentioned. Allah said in other Ayat,
فَإِن كَذَّبُوكَ فَقُل رَّبُّكُمْ ذُو رَحْمَةٍ وَسِعَةٍ وَلاَ يُرَدُّ بَأْسُهُ عَنِ الْقَوْمِ الْمُجْرِمِينَ
(If they belie you, say: "Your Lord is the Owner of vast mercy, and never will His wrath be turned back from the people who are criminals.")6:147
إِنَّ رَبَّكَ لَسَرِيعُ الْعِقَابِ وَإِنَّهُ لَغَفُورٌ رَّحِيمٌ
(Verily, your Lord is quick in retribution and certainly He is Oft-Forgiving, Most Merciful.)7:167, and,
نَبِّىءْ عِبَادِى أَنِّى أَنَا الْغَفُورُ الرَّحِيمُ - وَأَنَّ عَذَابِى هُوَ ٱلْعَذَابُ ٱلْأَلِيمُ
(Declare unto My servants that truly I am the Oft-Forgiving, the Most Merciful. And that My torment is indeed the most painful torment.)15:49-50 There are many other Ayat that mention both fear and hope.
وَيَقُولُ الَّذِينَ كَفَرُواْ لَوْلا أُنزِلَ عَلَيْهِ آيَةٌ مِّن رَّبِّهِ إِنَّمَآ أَنتَ مُنذِرٌ وَلِكُلِّ قَوْمٍ هَادٍ
Tafsir Ibn Kathir (abridged, English).