Salam
The last Surah to talk about reward is Surah Saad. There it ends and has some additions not found else where.
(1) It ends with the fact its a tiding we will know after a time. That is God is reminding us of the reality of his chosen ones, which is related to the reality of day of judgment and its truth. We will also know the value of their Authority and love and relationship to us then.
(2) It has a side comment "(and I am not of those who pretend)"
The "And I not of those who pretend" is unique here.
"It is only a reminder" is not unique, but it being linked to day of judgment is unique.
Let us see why this is the case and why these additions appear here.
ص ۚ وَالْقُرْآنِ ذِي الذِّكْرِ | By the name of God, the Compassionate (wide mercy), the Compassionate (intensely), Saad and by the Quran bearing the Reminder, | Saad : 1
It starts with the accusation:
وَعَجِبُوا أَنْ جَاءَهُمْ مُنْذِرٌ مِنْهُمْ ۖ وَقَالَ الْكَافِرُونَ هَٰذَا سَاحِرٌ كَذَّابٌ | They consider it odd that there should come to them a warner from among themselves, and the faithless say, ‘This is a sorcerer, a mendacious liar.’ | Saad : 4
So we see the "I am not of the pretentious" links back to this verse. But this Surah has a whole theme about this.
It talks about the reminder and their doubt, which links to the ending:
أَأُنْزِلَ عَلَيْهِ الذِّكْرُ مِنْ بَيْنِنَا ۚ بَلْ هُمْ فِي شَكٍّ مِنْ ذِكْرِي ۖ بَلْ لَمَّا يَذُوقُوا عَذَابِ | Has the Reminder been sent down to him out of [all of] us?’ Indeed, they are in doubt concerning My Reminder. Indeed, they have not yet tasted My punishment. | Saad : 8
This links it to the "They will come to know its tiding after some time"
The Quran also makes an argument:
أَمْ لَهُمْ مُلْكُ السَّمَاوَاتِ وَالْأَرْضِ وَمَا بَيْنَهُمَا ۖ فَلْيَرْتَقُوا فِي الْأَسْبَابِ | Do they have the authority of the heavens and the earth and whatever is between them? [If so,] let them ascend [to the higher spheres] by the means [of ascension]. | Saad : 10
And so pretentious cannot do that, while the true possess of the authority can. So we see again a link to the ending of it.
And it reminds of the past about accusation:
كَذَّبَتْ قَبْلَهُمْ قَوْمُ نُوحٍ وَعَادٌ وَفِرْعَوْنُ ذُو الْأَوْتَادِ | Before them Noah’s people impugned [their apostle] and [so did the people of] ‘Ad, and Pharaoh, the Impaler [of his victims], | Saad : 12
إِنْ كُلٌّ إِلَّا كَذَّبَ الرُّسُلَ فَحَقَّ عِقَابِ | There was not any one but such as impugned the apostles; so My retribution became due [against them]. | Saad : 14
And says:
وَمَا يَنْظُرُ هَٰؤُلَاءِ إِلَّا صَيْحَةً وَاحِدَةً مَا لَهَا مِنْ فَوَاقٍ | These [too] do not await but a single Cry, which will not grant [them] any respite. | Saad : 15
Then says:
وَقَالُوا رَبَّنَا عَجِّلْ لَنَا قِطَّنَا قَبْلَ يَوْمِ الْحِسَابِ | They say, ‘Our Lord! Hasten on for us our share before the Day of Reckoning.’ | Saad : 16
We see there is heavy emphasis on the accusation of being a liar and hastening punishment, before day of judgment.
اصْبِرْ عَلَىٰ مَا يَقُولُونَ وَاذْكُرْ عَبْدَنَا دَاوُودَ ذَا الْأَيْدِ ۖ إِنَّهُ أَوَّابٌ | Be patient over what they say, and remember Our servant, David, [the man] of strength. Indeed he was a penitent [soul]. | Saad : 17
Then it makes it impersonal and really that disbelievers believe the universe is created in vain and without purpose:
وَمَا خَلَقْنَا السَّمَاءَ وَالْأَرْضَ وَمَا بَيْنَهُمَا بَاطِلًا ۚ ذَٰلِكَ ظَنُّ الَّذِينَ كَفَرُوا ۚ فَوَيْلٌ لِلَّذِينَ كَفَرُوا مِنَ النَّارِ | We did not create the sky and the earth and whatever is between them in vain. That is a conjecture of the faithless. So woe to the faithless for the Fire! | Saad : 27
Then it shows, they do not want to distinguish between good and evil and follow their desires:
أَمْ نَجْعَلُ الَّذِينَ آمَنُوا وَعَمِلُوا الصَّالِحَاتِ كَالْمُفْسِدِينَ فِي الْأَرْضِ أَمْ نَجْعَلُ الْمُتَّقِينَ كَالْفُجَّارِ | Shall We treat those who have faith and do righteous deeds like those who cause corruption on the earth? Shall We treat the Godwary like the vicious? | Saad : 28
Then emphasizes the book is perceived by those who understand and they will remember:
كِتَابٌ أَنْزَلْنَاهُ إِلَيْكَ مُبَارَكٌ لِيَدَّبَّرُوا آيَاتِهِ وَلِيَتَذَكَّرَ أُولُو الْأَلْبَابِ | [This is] a blessed Book that We have sent down to you, so that they may contemplate its signs, and that those who possess intellect will be reminded. | Saad : 29
It also reminds of Sulaiman (a) and Dawood (a), but reminds that they were strengthen authority and it was for benefit of humanity. Therefore linking to fact if Mohammad (s) gains authority and his authority strengthened and his successors as well, then this is for the benefit of humanity.
So the reminder of Dawood (a) and Sulaiman (a) is also linked to reminding and arguing against the reward accusation.
قَالَ رَبِّ اغْفِرْ لِي وَهَبْ لِي مُلْكًا لَا يَنْبَغِي لِأَحَدٍ مِنْ بَعْدِي ۖ إِنَّكَ أَنْتَ الْوَهَّابُ | He said, ‘My Lord! Forgive me, and grant me a authority that will not befit anyone except me. Indeed You are the All-munificent.’ | Saad : 35
The authority was that of the type that forced devils to obey him, but we see force only increased people to accuse of sorcery. Sulaiman (a) wanted this authority to be one time and prove something with that.
And it emphasizes despite the material wealth and kingdom and authority he held on devils:
وَإِنَّ لَهُ عِنْدَنَا لَزُلْفَىٰ وَحُسْنَ مَآبٍ | Indeed he has [a station of] nearness with Us and a good destination. | Saad : 40
Regarding Ayub (a), it says:
وَوَهَبْنَا لَهُ أَهْلَهُ وَمِثْلَهُمْ مَعَهُمْ رَحْمَةً مِنَّا وَذِكْرَىٰ لِأُولِي الْأَلْبَابِ | We gave his family to him along with others like them, as a mercy from Us and a reminder for those who possess intellect. | Saad : 43
The chosen Ahlulbayt of his and those like them were a mercy from God and a reminder to those who possess intellect, and the chosen holy souls of his family were with Ayub (a) in his intense trials as well as other Ahlulbayts of the past.
This is again emphasize Ahlulbayts always exist, and so do not make it personal against Mohammad (s). You are denying ALL chosen ones, not just him.
Then goes on to emphasize on Ahlulbayt (a) of Ibrahim (a):
وَاذْكُرْ عِبَادَنَا إِبْرَاهِيمَ وَإِسْحَاقَ وَيَعْقُوبَ أُولِي الْأَيْدِي وَالْأَبْصَارِ | And remember Our servants, Abraham, Isaac and Jacob, men of strength and insight. | Saad : 45
Which are agreed upon by Jews, and for sake of argument left out Ismail (a).
إِنَّا أَخْلَصْنَاهُمْ بِخَالِصَةٍ ذِكْرَى الدَّارِ | Indeed We purified them with exclusive remembrance of the abode [of the Hereafter]. | Saad : 46
Showing they had no personal reward, because their reward lied in the next world with God.
وَإِنَّهُمْ عِنْدَنَا لَمِنَ الْمُصْطَفَيْنَ الْأَخْيَارِ | Indeed they are surely with Us among the chosen of those picked | Saad : 47
Then it reminds of Ismail (a) arguing for him, but reminds of Elyasa and his successor Dul-Kifl (peace be upon them two as well)
وَاذْكُرْ إِسْمَاعِيلَ وَالْيَسَعَ وَذَا الْكِفْلِ ۖ وَكُلٌّ مِنَ الْأَخْيَارِ | And remember Ishmael, Elisha and Dhu’l-Kifl—each [of whom was] among the elect. | Saad : 48
I talked about this specific verse before, and why Dul-Kifl is mentioned here with Alyasa, these two Prophets appear twice in the Quran, and here they appear together to emphasize succession to one another. And this reminds that Mohammad (s) does not come alone, but will have later successors as well.
It reminds that misguiding elites always bring people to hell, this goes with themes we saw earlier in other Surahs with respect to reward:
قَالُوا بَلْ أَنْتُمْ لَا مَرْحَبًا بِكُمْ ۖ أَنْتُمْ قَدَّمْتُمُوهُ لَنَا ۖ فَبِئْسَ الْقَرَارُ | They will say, ‘No, may wretchedness be your lot! You prepared this [hell] for us. What an evil abode!’ | Saad : 60
قَالُوا رَبَّنَا مَنْ قَدَّمَ لَنَا هَٰذَا فَزِدْهُ عَذَابًا ضِعْفًا فِي النَّارِ | They will say, ‘Our Lord! Whoever has prepared this for us, double his punishment in the Fire!’ | Saad : 61
Then it brings a huge argument in that disbelievers do not recognize good and evil, and will see no one they use to count among the evil from the friends of God:
وَقَالُوا مَا لَنَا لَا نَرَىٰ رِجَالًا كُنَّا نَعُدُّهُمْ مِنَ الْأَشْرَارِ | And they will say, ‘Why is it that we do not see [here] men whom we used to count among the bad ones? | Saad : 62
أَتَّخَذْنَاهُمْ سِخْرِيًّا أَمْ زَاغَتْ عَنْهُمُ الْأَبْصَارُ | ridiculing them, or do [our] eyes miss them [here]?’ | Saad : 63
The word tiding also appears, then says:
مَا كَانَ لِيَ مِنْ عِلْمٍ بِالْمَلَإِ الْأَعْلَىٰ إِذْ يَخْتَصِمُونَ | I have no knowledge of the Supernal Elite when they contended. | Saad : 69
Then reminds the most highest/exalted council was souls who did not need to prostrate to Adam (a):
قَالَ يَا إِبْلِيسُ مَا مَنَعَكَ أَنْ تَسْجُدَ لِمَا خَلَقْتُ بِيَدَيَّ ۖ أَسْتَكْبَرْتَ أَمْ كُنْتَ مِنَ الْعَالِينَ | He said, ‘O Iblis! What keeps you from prostrating before that which I have created with My [own] two hands? Are you arrogant, or are you one of the exalted ones?’ | Saad : 75
And so we see in makes the argument, that disbelievers can not distinguish between good and evil and acting similarly as Iblis did with Adam with respect to the exalted ones who Mohammad (s) is one of.
So we see the ending of the Surah:
قُلْ مَا أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ وَمَا أَنَا مِنَ الْمُتَكَلِّفِينَ
Say: what reward do I ask of it - and I am not of the pretentious -
إِنْ هُوَ إِلَّا ذِكْرٌ لِلْعَالَمِينَ
In that is only a reminder to the worlds?
وَلَتَعْلَمُنَّ نَبَأَهُ بَعْدَ حِينٍ
And you will know of it's tiding after a time.
Is again very well suited for the Surah. In fact, the "and I am not the pretentious" and the ending of reward shows this an important theme. And it emphasizes what has been emphasized through out the Surah and links to the reward.
And it links it to the promise of destruction with the Mahdi (a) as well as Day of judgment, when we realize the favor Mohammad (a) and his exalted family (a) are and were, and will know of its reality then and how connected to God it was.
The final line also links back to:
قُلْ هُوَ نَبَأٌ عَظِيمٌ | Say, ‘It is a great tiding, | Saad : 67
أَنْتُمْ عَنْهُ مُعْرِضُونَ | of which you are turning away from | Saad : 68
Showing the Quran is reminding of Ahlulbayt (a) and Ahlulbayt (a) remind of Quran, together, they are one reminder and their light reality, power, and sky lanterns weapon reality, is linked to the day of judgment as well.
The fact these verses were put at the ending also shows the whole Surah flowing to it.
And going back to start:
ص ۚ وَالْقُرْآنِ ذِي الذِّكْرِ | By the name of God, the Compassionate (wide mercy), the Compassionate (intensely), Saad and by the Quran bearing the Reminder, | Saad : 1
It proves indeed:
بَلِ الَّذِينَ كَفَرُوا فِي عِزَّةٍ وَشِقَاقٍ | the faithless indeed dwell in conceit and defiance. | Saad : 2