In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Allaah [The Most High] informed us that Fir’awn said:
[أَمۡ أَنَا۟ خَيۡرٌ۬ مِّنۡ هَـٰذَا ٱلَّذِى هُوَ مَهِينٌ۬ وَلَا يَكَادُ يُبِينُ – Am I not better than this one [Musa (Moses)], who is Mahin [has no honour nor any respect, and is weak and despicable] and can scarcely express himself clearly?][Surah Az-Zukhruf’ Ayah 52]
Imaam As-Sadi [rahimahullaa] said:
May Allaah [The Most High] disfigure Fir’awn, for indeed he intended Moosaa [alayhis-salaam] by this description, even though Moosaa [alayhis-salaam] is one whom Allaah [The Most High] spoke to directly and one given high status by Allaah [The Most High]; however Fir’awn thought that he is honoured and Moosaa [alayhis-salaam] is dishonoured and disgraced. He also proclaimed that in addition to this, Moosaa [alayhis-salaam] cannot even speak clearly because he is not eloquent! However, Firawn’s insult against Moosaa [alayhis-salaam] -that Moosaa cannot even express himself- is not something blameworthy at all. That is because Moosaa [alayhis-salaam] was able to convey the message, even though he used encounter some difficulty when speaking.
[Source: Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer Kalaam Al-Mannaan. abridged & slightly paraphrased]