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

Allaah [The Most High] says that Fir’awn, his chiefs and blind followers said:

[ مَهۡمَا تَأۡتِنَا بِهِۦ مِنۡ ءَايَةٍ۬ لِّتَسۡحَرَنَا بِہَا فَمَا نَحۡنُ لَكَ بِمُؤۡمِنِينَ- Whatever Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) you may bring to us, to work therewith your sorcery on us, we shall never believe in you]: Meaning: They made it clear to Prophet Musa that they will not cease to be upon their false path. That is because- as they claimed- Prophet Musa is a magician, so regardless what he showed them, they will consider it to be magic. Indeed, this is a state of extreme obstinacy- when disbelievers reach that state of disbelief in which they care less whether clear signs have been shown to them or not!

Then Allaah [The Most High] said: [فَأَرۡسَلۡنَا عَلَيۡہِمُ ٱلطُّوفَانَ  – So We sent on them: the flood]; meaning: Abundant water that destroyed their trees and vegetation, and brought about extreme hardship; [وَٱلۡجَرَادَ – the locusts] that ate their crops; [وَٱلۡقُمَّلَ– the lice]: [وَٱلضَّفَادِعَ  – the frogs] that entered into their springs in great numbers and caused them extreme anxiety; [وَٱلدَّمَ  – and the blood]: Meaning: their drinking water was turned into blood.  [ءَايَـٰتٍ۬ مُّفَصَّلَـٰتٍ۬ – (as a succession of) manifest signs]: Meaning: These were clear signs that made it clear to them that they have rejected the truth and are transgressors.  [فَٱسۡتَڪۡبَرُواْ وَكَانُواْ قَوۡمً۬ا مُّجۡرِمِينَ – yet they remained arrogant, and they were of those people who were Mujrimun (criminals, polytheists, sinners, etc.)]: Meaning: After they saw all these signs, they were still haughty, so Allaah left them upon their deviation and misguidance.

[An Excerpt from ‘Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer kalaam Al-Mannaan’ of Imaam As-Sadi (rahimahullaah)]