In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
In Surah Yunus, Allaah [The Most High] informed us about Nuh [alayhis salaam] and the evil end of those who rejected his message of Tawheed; then Allaah [The Most High] informed us that He sent Messengers after Nuh [alayhis-salaam]; Allaah said:
ثُمَّ بَعَثۡنَا مِنۢ بَعۡدِهِۦ رُسُلاً إِلَىٰ قَوۡمِهِمۡ فَجَآءُوهُم بِٱلۡبَيِّنَـٰتِ فَمَا كَانُواْ لِيُؤۡمِنُواْ بِمَا كَذَّبُواْ بِهِۦ مِن قَبۡلُۚ كَذَٲلِكَ نَطۡبَعُ عَلَىٰ قُلُوبِ ٱلۡمُعۡتَدِينَ
Then after him We sent Messengers to their people, they brought them clear proofs, but they would not believe what they had already rejected beforehand. Thus We seal the hearts of the transgressors (those who disbelieve in the Oneness of Allah and disobey Him). [10:74]
Then Allaah [The Most High] informed us that He sent Moosaa and Haaroon [alayhimas-salaam] to Fir’awn and his people. Allaah [The Most High] said:
ثُمَّ بَعَثۡنَا مِنۢ بَعۡدِهِم مُّوسَىٰ وَهَـٰرُونَ إِلَىٰ فِرۡعَوۡنَ وَمَلَإِيْهِۦ بِـَٔايَـٰتِنَا فَٱسۡتَكۡبَرُواْ وَكَانُواْ قَوۡمً۬ا مُّجۡرِمِينَ فَلَمَّا جَآءَهُمُ ٱلۡحَقُّ مِنۡ عِندِنَا قَالُوٓاْ إِنَّ هَـٰذَا لَسِحۡرٌ۬ مُّبِينٌ۬
Then after them We sent Musa (Moses) and Harun (Aaron) to Fir’aun (Pharaoh) and his chiefs with Our Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.). But they behaved arrogantly and were Mujrimun (criminals etc)
After the departure of the Messengers-those who were sent to the previous destroyed nations, Allaah sent Moosaa Ibn Imraan [alayhis-salaam]- a Messenger whom Allaah spoke to directly, a Messenger amongst the five Messengers of firm resolve, those taken as perfect examples to follow and to whom were revealed the great and comprehensive divine laws. Allaah [The Most High] also appointed Moosaa’s brother-Haaroon as a Messenger and Moosaa’s deputy, and sent both of them to Fir’awn and his chiefs – the senior people and leaders of Fir’awn’s Kingdom- because they were the ones followed by the common people.
Allaah gave Moosaa and Haaroon clear proofs- manifesting the fact that Allaah alone is the Lord of the entire creation, the possessor of Perfect Names and Attributes and the only deity worthy of worship; however Fir’awn and his chiefs turned away from those proofs wrongfully and arrogantly after being certain of the truth, because they were a people given to criminality. When the proofs came to them, they said that it was tantamount to manifest magic! Therefore, not only did they reject the truth; rather they also attributed it to magic -the falsest of falsehoods -whose reality is nothing else but concealment of truth. And because of this statement of theirs, Allaah [The Most High] said that Moosaa (alayhis-salaam) said to them:
قَالَ مُوسَىٰٓ أَتَقُولُونَ لِلۡحَقِّ لَمَّا جَآءَڪُمۡۖ أَسِحۡرٌ هَـٰذَا وَلَا يُفۡلِحُ ٱلسَّـٰحِرُونَ
Musa (Moses) said: “Say you (this) about the truth when it has come to you? Is this magic? But the magicians will never be successful.” [10:77]
A magician will never be successful- neither in this life nor in the afterlife. And indeed it has become manifest to everyone that Moosaa [alayhis-salaam] was the one who succeeded.
Then Allaah [The Most High] said that Fir’awn and his chiefs said:
قَالُوٓاْ أَجِئۡتَنَا لِتَلۡفِتَنَا عَمَّا وَجَدۡنَا عَلَيۡهِ ءَابَآءَنَا وَتَكُونَ لَكُمَا ٱلۡكِبۡرِيَآءُ فِى ٱلۡأَرۡضِ وَمَا نَحۡنُ لَكُمَا بِمُؤۡمِنِينَ
They said: “Have you come to us to turn us away from that (Faith) we found our fathers following, – and that you two may have greatness in the land? We are not going to believe you two!” [10:78]
They meant: Have you [O Moosaa] come to us to hinder us from what our forefathers were upon- the religion of shirk- and then command us to worship Allaah alone? So they argued in this manner and used their misguided forefathers as proof by way of which they rejected what Moosaa brought to them. They also said that both Moosaa and Haaroon only came to them with the message of Tawheed because they desired leadership and to expel them from their land! Fir’awn and his chiefs made this claim in order to conceal the truth, spread propaganda amongst their ignorant people, incite [enmity in the hearts of the people] against Moosaa and prevent them from believing in him.
Indeed, the one who is acquainted with the reality knows that this argument of theirs is neither a proof nor a distinction between truth and falsehood- because proofs cannot be nullified except with stronger proofs and evidences. The one who presents the truth and is rejected through the likes of these arguments [uttered by Fir’awn and his chiefs] has indeed established the fact that his opponent is unable to produce a robust refutation; for if his opponent had any clear proofs he would have presented them and would not merely say that he intends or wants such and such- regardless whether this claim is right or wrong. On the other hand, everyone who is acquainted with Moosaa’s [alayhis-salaam] state of affairs and what he conveyed knows that his intention was not to become exalted in the land; rather his intention – and that of his brothers amongst the Messengers of Allaah -was to guide the people and direct them to what will benefit them in this life and the hereafter. However, the behaviour of Fir’awn and his chiefs cannot be described in any other way other than what Allaah has stated that they said: [وَمَا نَحۡنُ لَكُمَا بِمُؤۡمِنِينَ – We are not going to believe you two!].
This rejection of theirs was due to pride and obstinacy, but neither because what Moosaa and Haaroon conveyed was false nor ambiguous; rather they rejected what Moosaa and Haaroon conveyed due to arrogance and transgression- a desire to be exalted, which they sought to falsely accuse Moosaa and Haaroon of.
[Source: An Excerpt from ‘Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer Kalaam Al-Mannaan’ by Imaam As-Sadi (rahimahullaah)]