Messengers from God would not seek wealth from the people, because, it can be looked as something they gain. However, even if they didn't seek wealth from people, they can be accused of being greedy for power, fame, authority, kingship, etc...
While disbelievers saw that they sought "reward" - God knew they didn't, as God was the best of those who provide sustenance. However, God described the reward people saw them seeking and put a defense to it in Quran.
1. The reward as a reminder in Suratal Ana'aam
In this chapter, we are reminded of God's light and the darkness, and we see how dark and evil can be the result of being mislead by devils and their authorities from humans.
In reminding of the Messengers:
وَتِلْكَ حُجَّتُنَا آتَيْنَاهَا إِبْرَاهِيمَ عَلَىٰ قَوْمِهِ ۚ نَرْفَعُ دَرَجَاتٍ مَنْ نَشَاءُ ۗ إِنَّ رَبَّكَ حَكِيمٌ عَلِيمٌ {83}
[Shakir 6:83] And this was Our argument which we gave to Ibrahim against his people; We exalt in dignity whom We please; surely your Lord is Wise, Knowing.
وَوَهَبْنَا لَهُ إِسْحَاقَ وَيَعْقُوبَ ۚ كُلًّا هَدَيْنَا ۚ وَنُوحًا هَدَيْنَا مِنْ قَبْلُ ۖ وَمِنْ ذُرِّيَّتِهِ دَاوُودَ وَسُلَيْمَانَ وَأَيُّوبَ وَيُوسُفَ وَمُوسَىٰ وَهَارُونَ ۚ وَكَذَٰلِكَ نَجْزِي الْمُحْسِنِينَ {84}
[Shakir 6:84] And We gave to him Ishaq and Yaqoub; each did We guide, and Nuh did We guide before, and of his descendants, Dawood and Sulaiman and Ayub and Yusuf and Haroun; and thus do We reward those who do good (to others).
وَزَكَرِيَّا وَيَحْيَىٰ وَعِيسَىٰ وَإِلْيَاسَ ۖ كُلٌّ مِنَ الصَّالِحِينَ {85}
[Shakir 6:85] And Zakariya and Yahya and Isa and Ilyas; every one was of the good;
وَإِسْمَاعِيلَ وَالْيَسَعَ وَيُونُسَ وَلُوطًا ۚ وَكُلًّا فَضَّلْنَا عَلَى الْعَالَمِينَ {86}
[Shakir 6:86] And Ismail and Al-Yasha and Yunus and Lut; and every one We made to excel (in) the worlds:
وَمِنْ آبَائِهِمْ وَذُرِّيَّاتِهِمْ وَإِخْوَانِهِمْ ۖ وَاجْتَبَيْنَاهُمْ وَهَدَيْنَاهُمْ إِلَىٰ صِرَاطٍ مُسْتَقِيمٍ {87}
[Shakir 6:87] And from among their fathers and their descendants and their brethren, and We chose them and guided them into the right way.
ذَٰلِكَ هُدَى اللَّهِ يَهْدِي بِهِ مَنْ يَشَاءُ مِنْ عِبَادِهِ ۚ وَلَوْ أَشْرَكُوا لَحَبِطَ عَنْهُمْ مَا كَانُوا يَعْمَلُونَ {88}
[Shakir 6:88] This is Allah's guidance, He guides thereby whom He pleases of His servants; and if they had set up others (with Him), certainly what they did would have become ineffectual for them.
أُولَٰئِكَ الَّذِينَ آتَيْنَاهُمُ الْكِتَابَ وَالْحُكْمَ وَالنُّبُوَّةَ ۚ فَإِنْ يَكْفُرْ بِهَا هَٰؤُلَاءِ فَقَدْ وَكَّلْنَا بِهَا قَوْمًا لَيْسُوا بِهَا بِكَافِرِينَ {89}
[Shakir 6:89] These are they to whom We gave the book and the wisdom and the prophecy; therefore if these disbelieve in it We have already entrusted with it a people who are not disbelievers in it.
أُولَٰئِكَ الَّذِينَ هَدَى اللَّهُ ۖ فَبِهُدَاهُمُ اقْتَدِهْ ۗ قُلْ لَا أَسْأَلُكُمْ عَلَيْهِ أَجْرًا ۖ إِنْ هُوَ إِلَّا ذِكْرَىٰ لِلْعَالَمِينَ {90}
[6:90] These are they whom Allah guided, therefore follow their guidance. Say: I do not ask you for any reward for it that it is only a reminder to the nations.
In being reminded of the chosen ones, we are reminded that what Mohammad is seen as seeking as a reward is in fact a reminder to the worlds because Mohammad's love and following him and honoring him and him being famous is all a reminder to the worlds of the light of God and guidance.
In this first place, it's also emphasized that the chosen ones were related by kinship. So power, fame, leadership, authority, control, etc, that people saw Prophets seeking reward by claiming Prophethood, it is said this what you accuse him, if it's the truth, would be but a reminder to the worlds. But aside from this, they were seen to favor their kin and bloodline after.
And here we see the Quran is emphasizing that yes chosen ones came out of the offspring of Noah and of Abraham, but there was a wisdom. Keep this in mind when coming to 42:23.
Here we see it's arguing these chosen ones are the ones who God guided and yes guidance of God was placed in their offspring and the guides were chosen from their offspring and God directly guided these souls and we can get guided by following them and being inspired by them and hence, what people see the Prophets gaining as a reward is a necessity, because, it's the way God guides.
2. The reward as a reminder in Suratal Yusuf
In this chapter, the story of Joseph/Yusuf occurs in which the theme of chosen family and the guidance in them is obvious. The brothers of Joseph except Benjamin, were not chosen however they do repent. Joseph and being in the offspring of Isaac, has a complete manifest wisdom in this chapter. Consequently, the chosen ones remembrance, fame, position, even if it reaches political authority as it did eventually with Joseph, is for the benefit of humans. Believers honoring these chosen ones, it's for their benefit, as we see the brothers of Joseph redeemed by honoring Joseph. It ends with reflections among them reminding of the fact:
وَمَا تَسْأَلُهُمْ عَلَيْهِ مِنْ أَجْرٍ ۚ إِنْ هُوَ إِلَّا ذِكْرٌ لِلْعَالَمِينَ {104}
[12:104] And you do not seek from them a reward in that it is only a reminder to the worlds.
3. The reward is actually a call to the straight path in Suratal Mominoon
After reminding of how Messengers guided humans and the honor of believers gained through them and also the chaos and oppression that occurs when their opponents are followed instead.
[23:72]Or do you ask them a recompense? For the recompense of your Lord is better and he is the best of those who provide sustenance.
[23:73]And verily you call them to a straight path.
4. The reward as a path to God in Suratal Furqan.
This chapter it emphasizes on people complaining about the humanity of the Messenger Mohammad and also their looking down upon him.
وَقَالُوا مَالِ هَٰذَا الرَّسُولِ يَأْكُلُ الطَّعَامَ وَيَمْشِي فِي الْأَسْوَاقِ ۙ لَوْلَا أُنْزِلَ إِلَيْهِ مَلَكٌ فَيَكُونَ مَعَهُ نَذِيرًا {7}
[Shakir 25:7] And they say: What is the matter with this Messenger that he eats food and goes about in the markets; why has not an angel been sent down to him, so that he should have been a warner with him?
أَوْ يُلْقَىٰ إِلَيْهِ كَنْزٌ أَوْ تَكُونُ لَهُ جَنَّةٌ يَأْكُلُ مِنْهَا ۚ وَقَالَ الظَّالِمُونَ إِنْ تَتَّبِعُونَ إِلَّا رَجُلًا مَسْحُورًا {8}
[Shakir 25:8] Or (why is not) a treasure sent down to him, or he is made to have a garden from which he should eat? And the unjust say: You do not follow any but a man deprived of reason.
انْظُرْ كَيْفَ ضَرَبُوا لَكَ الْأَمْثَالَ فَضَلُّوا فَلَا يَسْتَطِيعُونَ سَبِيلًا {9}
[Shakir 25:9] See what likenesses do they apply to you, so they have gone astray, therefore they shall not be able to find a way.
وَيَوْمَ يَعَضُّ الظَّالِمُ عَلَىٰ يَدَيْهِ يَقُولُ يَا لَيْتَنِي اتَّخَذْتُ مَعَ الرَّسُولِ سَبِيلًا {27}
[Shakir 25:27] And the day when the unjust one shall bite his hands saying: O! would that I had taken a way with the Messenger
In this context of Mohammad and past Messengers being the way and path, it emphasizes:
قُلْ مَا أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ إِلَّا مَنْ شَاءَ أَنْ يَتَّخِذَ إِلَىٰ رَبِّهِ سَبِيلًا {57}
[25:57]Say: what reward do I ask for it except who wants to, to take to their Lord a path?
Then the following verse emphasizes when they are obeying the Messengers, they are obeying God, but the disbelievers see submitting and prostrating to God as submitting to the commands of Mohammad as well as them acknowledging the Compassionate Lord of the universe and his traits and titles as submission to Mohammad:
وَإِذَا قِيلَ لَهُمُ اسْجُدُوا لِلرَّحْمَٰنِ قَالُوا وَمَا الرَّحْمَٰنُ أَنَسْجُدُ لِمَا تَأْمُرُنَا وَزَادَهُمْ نُفُورًا
[25:60] And when it is said to them: Prostrate to the Compassionate, they say: And what is the Compassionate? Shall we prostrate to what you bid us? And it adds to their aversion.
In then goes on to remind of who the servants of God that God chooses for guidance are. It's obviously here suggesting, what people see as a reward on Mohammad part, what is that, really, but a path to God?
While disbelievers saw that they sought "reward" - God knew they didn't, as God was the best of those who provide sustenance. However, God described the reward people saw them seeking and put a defense to it in Quran.
1. The reward as a reminder in Suratal Ana'aam
In this chapter, we are reminded of God's light and the darkness, and we see how dark and evil can be the result of being mislead by devils and their authorities from humans.
In reminding of the Messengers:
وَتِلْكَ حُجَّتُنَا آتَيْنَاهَا إِبْرَاهِيمَ عَلَىٰ قَوْمِهِ ۚ نَرْفَعُ دَرَجَاتٍ مَنْ نَشَاءُ ۗ إِنَّ رَبَّكَ حَكِيمٌ عَلِيمٌ {83}
[Shakir 6:83] And this was Our argument which we gave to Ibrahim against his people; We exalt in dignity whom We please; surely your Lord is Wise, Knowing.
وَوَهَبْنَا لَهُ إِسْحَاقَ وَيَعْقُوبَ ۚ كُلًّا هَدَيْنَا ۚ وَنُوحًا هَدَيْنَا مِنْ قَبْلُ ۖ وَمِنْ ذُرِّيَّتِهِ دَاوُودَ وَسُلَيْمَانَ وَأَيُّوبَ وَيُوسُفَ وَمُوسَىٰ وَهَارُونَ ۚ وَكَذَٰلِكَ نَجْزِي الْمُحْسِنِينَ {84}
[Shakir 6:84] And We gave to him Ishaq and Yaqoub; each did We guide, and Nuh did We guide before, and of his descendants, Dawood and Sulaiman and Ayub and Yusuf and Haroun; and thus do We reward those who do good (to others).
وَزَكَرِيَّا وَيَحْيَىٰ وَعِيسَىٰ وَإِلْيَاسَ ۖ كُلٌّ مِنَ الصَّالِحِينَ {85}
[Shakir 6:85] And Zakariya and Yahya and Isa and Ilyas; every one was of the good;
وَإِسْمَاعِيلَ وَالْيَسَعَ وَيُونُسَ وَلُوطًا ۚ وَكُلًّا فَضَّلْنَا عَلَى الْعَالَمِينَ {86}
[Shakir 6:86] And Ismail and Al-Yasha and Yunus and Lut; and every one We made to excel (in) the worlds:
وَمِنْ آبَائِهِمْ وَذُرِّيَّاتِهِمْ وَإِخْوَانِهِمْ ۖ وَاجْتَبَيْنَاهُمْ وَهَدَيْنَاهُمْ إِلَىٰ صِرَاطٍ مُسْتَقِيمٍ {87}
[Shakir 6:87] And from among their fathers and their descendants and their brethren, and We chose them and guided them into the right way.
ذَٰلِكَ هُدَى اللَّهِ يَهْدِي بِهِ مَنْ يَشَاءُ مِنْ عِبَادِهِ ۚ وَلَوْ أَشْرَكُوا لَحَبِطَ عَنْهُمْ مَا كَانُوا يَعْمَلُونَ {88}
[Shakir 6:88] This is Allah's guidance, He guides thereby whom He pleases of His servants; and if they had set up others (with Him), certainly what they did would have become ineffectual for them.
أُولَٰئِكَ الَّذِينَ آتَيْنَاهُمُ الْكِتَابَ وَالْحُكْمَ وَالنُّبُوَّةَ ۚ فَإِنْ يَكْفُرْ بِهَا هَٰؤُلَاءِ فَقَدْ وَكَّلْنَا بِهَا قَوْمًا لَيْسُوا بِهَا بِكَافِرِينَ {89}
[Shakir 6:89] These are they to whom We gave the book and the wisdom and the prophecy; therefore if these disbelieve in it We have already entrusted with it a people who are not disbelievers in it.
أُولَٰئِكَ الَّذِينَ هَدَى اللَّهُ ۖ فَبِهُدَاهُمُ اقْتَدِهْ ۗ قُلْ لَا أَسْأَلُكُمْ عَلَيْهِ أَجْرًا ۖ إِنْ هُوَ إِلَّا ذِكْرَىٰ لِلْعَالَمِينَ {90}
[6:90] These are they whom Allah guided, therefore follow their guidance. Say: I do not ask you for any reward for it that it is only a reminder to the nations.
In being reminded of the chosen ones, we are reminded that what Mohammad is seen as seeking as a reward is in fact a reminder to the worlds because Mohammad's love and following him and honoring him and him being famous is all a reminder to the worlds of the light of God and guidance.
In this first place, it's also emphasized that the chosen ones were related by kinship. So power, fame, leadership, authority, control, etc, that people saw Prophets seeking reward by claiming Prophethood, it is said this what you accuse him, if it's the truth, would be but a reminder to the worlds. But aside from this, they were seen to favor their kin and bloodline after.
And here we see the Quran is emphasizing that yes chosen ones came out of the offspring of Noah and of Abraham, but there was a wisdom. Keep this in mind when coming to 42:23.
Here we see it's arguing these chosen ones are the ones who God guided and yes guidance of God was placed in their offspring and the guides were chosen from their offspring and God directly guided these souls and we can get guided by following them and being inspired by them and hence, what people see the Prophets gaining as a reward is a necessity, because, it's the way God guides.
2. The reward as a reminder in Suratal Yusuf
In this chapter, the story of Joseph/Yusuf occurs in which the theme of chosen family and the guidance in them is obvious. The brothers of Joseph except Benjamin, were not chosen however they do repent. Joseph and being in the offspring of Isaac, has a complete manifest wisdom in this chapter. Consequently, the chosen ones remembrance, fame, position, even if it reaches political authority as it did eventually with Joseph, is for the benefit of humans. Believers honoring these chosen ones, it's for their benefit, as we see the brothers of Joseph redeemed by honoring Joseph. It ends with reflections among them reminding of the fact:
وَمَا تَسْأَلُهُمْ عَلَيْهِ مِنْ أَجْرٍ ۚ إِنْ هُوَ إِلَّا ذِكْرٌ لِلْعَالَمِينَ {104}
[12:104] And you do not seek from them a reward in that it is only a reminder to the worlds.
3. The reward is actually a call to the straight path in Suratal Mominoon
After reminding of how Messengers guided humans and the honor of believers gained through them and also the chaos and oppression that occurs when their opponents are followed instead.
[23:72]Or do you ask them a recompense? For the recompense of your Lord is better and he is the best of those who provide sustenance.
[23:73]And verily you call them to a straight path.
4. The reward as a path to God in Suratal Furqan.
This chapter it emphasizes on people complaining about the humanity of the Messenger Mohammad and also their looking down upon him.
وَقَالُوا مَالِ هَٰذَا الرَّسُولِ يَأْكُلُ الطَّعَامَ وَيَمْشِي فِي الْأَسْوَاقِ ۙ لَوْلَا أُنْزِلَ إِلَيْهِ مَلَكٌ فَيَكُونَ مَعَهُ نَذِيرًا {7}
[Shakir 25:7] And they say: What is the matter with this Messenger that he eats food and goes about in the markets; why has not an angel been sent down to him, so that he should have been a warner with him?
أَوْ يُلْقَىٰ إِلَيْهِ كَنْزٌ أَوْ تَكُونُ لَهُ جَنَّةٌ يَأْكُلُ مِنْهَا ۚ وَقَالَ الظَّالِمُونَ إِنْ تَتَّبِعُونَ إِلَّا رَجُلًا مَسْحُورًا {8}
[Shakir 25:8] Or (why is not) a treasure sent down to him, or he is made to have a garden from which he should eat? And the unjust say: You do not follow any but a man deprived of reason.
انْظُرْ كَيْفَ ضَرَبُوا لَكَ الْأَمْثَالَ فَضَلُّوا فَلَا يَسْتَطِيعُونَ سَبِيلًا {9}
[Shakir 25:9] See what likenesses do they apply to you, so they have gone astray, therefore they shall not be able to find a way.
وَيَوْمَ يَعَضُّ الظَّالِمُ عَلَىٰ يَدَيْهِ يَقُولُ يَا لَيْتَنِي اتَّخَذْتُ مَعَ الرَّسُولِ سَبِيلًا {27}
[Shakir 25:27] And the day when the unjust one shall bite his hands saying: O! would that I had taken a way with the Messenger
In this context of Mohammad and past Messengers being the way and path, it emphasizes:
قُلْ مَا أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ إِلَّا مَنْ شَاءَ أَنْ يَتَّخِذَ إِلَىٰ رَبِّهِ سَبِيلًا {57}
[25:57]Say: what reward do I ask for it except who wants to, to take to their Lord a path?
Then the following verse emphasizes when they are obeying the Messengers, they are obeying God, but the disbelievers see submitting and prostrating to God as submitting to the commands of Mohammad as well as them acknowledging the Compassionate Lord of the universe and his traits and titles as submission to Mohammad:
وَإِذَا قِيلَ لَهُمُ اسْجُدُوا لِلرَّحْمَٰنِ قَالُوا وَمَا الرَّحْمَٰنُ أَنَسْجُدُ لِمَا تَأْمُرُنَا وَزَادَهُمْ نُفُورًا
[25:60] And when it is said to them: Prostrate to the Compassionate, they say: And what is the Compassionate? Shall we prostrate to what you bid us? And it adds to their aversion.
In then goes on to remind of who the servants of God that God chooses for guidance are. It's obviously here suggesting, what people see as a reward on Mohammad part, what is that, really, but a path to God?