In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Allaah [The Most High] said that Moosaa [alayhis-salaam] said:

رَبَّنَآ إِنَّكَ ءَاتَيۡتَ فِرۡعَوۡنَ وَمَلَأَهُ ۥ زِينَةً۬ وَأَمۡوَٲلاً۬ فِى ٱلۡحَيَوٰةِ ٱلدُّنۡيَا رَبَّنَا لِيُضِلُّواْ عَن سَبِيلِكَ‌ۖ

Our Lord! You have indeed bestowed on Fir’aun (Pharaoh) and his chiefs splendour and wealth in the life of this world, our Lord! That they may lead men astray from Your Path(10:88)]; Meaning: Splendour by way of which they beauty themselves with various types of clothing, and likewise they have beautiful houses, riding beasts, servants and tremendous wealth in the life of this world, which they utilise to misguide people from Your Path- misguided and misguiding others.

رَبَّنَا ٱطۡمِسۡ عَلَىٰٓ أَمۡوَٲلِهِمۡ وَٱشۡدُدۡ عَلَىٰ قُلُوبِهِمۡ فَلَا يُؤۡمِنُواْ حَتَّىٰ يَرَوُاْ ٱلۡعَذَابَ ٱلۡأَلِيمَ

Our Lord! Destroy their wealth, and harden their hearts, so that they will not believe until they see the painful torment. [10:88].

Moosaa made this supplication against them because they transgressed against Allaah’s commandments, corrupted the slaves of Allaah and hindered them from the path of Allaah. So Allaah [The Most High] said to Moosaa and Haaroon [alayhismas-salaam]: [قَدۡ أُجِيبَت دَّعۡوَتُڪُمَا -Verily, the invocation of you both is accepted]; This shows that Moosaa used to supplicate and Haaroon used to say Aameen to his supplication, and the one who says Aameen to a supplication shares what is within that supplication.

[فَٱسۡتَقِيمَا وَلَا تَتَّبِعَآنِّ سَبِيلَ ٱلَّذِينَ لَا يَعۡلَمُونَ – So you both keep to the Straight Way, and follow not the path of those who know not]; Meaning: Adhere to your religion and keep on supplicating. And do not follow the path of the misguided people – those who have deviated from the straight path and follow paths leading to the hell fire.

[Source: An Excerpt from ‘Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer Kalaam Al-Mannaan’ by Imaam As-Sadi (rahimahullaah)]