Is it true that the prayer of Prophet Moses against Pharaoh was not answered until after forty years due to Pharaoh's kindness to his mother, and that the prayer was answered after her death?

Allah Almighty says: (And Moses said, "Our Lord, indeed You have given Pharaoh and his establishment splendor and wealth in the worldly life, our Lord, that they may lead [people] astray from Your way. Our Lord, obliterate their wealth and harden their hearts so that they will not believe until they see the painful punishment." [Allah] said, "Your supplication has been answered. So remain on the right course and do not follow the way of those who do not know.") [Quran 10:88-89]. It has been narrated that the period between Moses' supplication against Pharaoh and Allah's response was forty years.

There is no validity to what is mentioned about Pharaoh's kindness to his mother or any other positive news, for he is known for his tyranny and arrogance on earth. The delay in his punishment after the supplication of Moses and Aaron, peace be upon them – if true – was a matter of Allah's granting him and his people respite to increase them in sin and magnify their punishment, as Allah Almighty said: (Indeed, Allah grants respite to the oppressor, but when He seizes him, He does not let him escape.) [Al-Bukhari]. Among the wisdoms of delaying punishment is also the testing of the believers and the destruction of the disbelievers.