Fir'awn said: "And what is the Lord of Al-'Alamin (23)(Musa) said: "The Lord of the heavens and the earth, and all that is between them, if you seek to be convinced with certainty. (24)(Fir'awn) said to those around: "Do you not hear (what he says)? (25)(Musa) said: "Your Lord and the Lord of your ancient fathers! (26)(Fir'awn) said: "Verily, your Messenger who has been sent to you is a madman! (27)(Musa) said: "Lord of the east and the west, and all that is between them, if you did but understand! (28)

وَمَا رَبُّ الْعَالَمِينَ

((Fir'awn said:) "And what is the Lord of the 'Alamin") This is because he used to say to his people:

مَا عَلِمْتُ لَكُم مِّنْ إِلَٰهٍ غَيْرِي 

(I know not that you have a god other than me.)(28:38)

فَاسْتَخَفَّ قَوْمَهُ فَأَطَاعُوهُ

(Thus he fooled his people, and they obeyed him.)(43:54) They used to deny the Creator, may He be glorified, and they believed that they had no other lord than Fir'awn. When Musa said to them: "I am the Messenger of the Lord of the worlds," Fir'awn said to him, "Who is this who you are claiming is the Lord of Al-'Alamin other than me?" This is how it was interpreted by the scholars of the Salaf and the Imams of later generations. As-Suddi said, "This Ayah is like the Ayah,

قَالَ فَمَن رَّبُّكُمَا يَا مُوسَىٰ - قَالَ رَبُّنَا الَّذِي أَعْطَىٰ كُلَّ شَيْءٍ خَلْقَهُ ثُمَّ هَدَىٰ

((Fir'awn) said: "Who then, O Musa, is the Lord of you two?" He said: "Our Lord is He Who gave to each thing its form and nature, then guided it aright.")(20:49-50)

Those among the philosophers and others who claimed that this was a question about the nature or substance [of Allah] are mistaken. Fir'awn did not believe in the Creator in the first place, so he was in no position to ask about the nature of the Creator; he denied that the Creator existed at all, as is apparent from the meaning, even though proof and evidence had been established against him. When Fir'awn asked him about the Lord of Al-'Alamin, Musa said:

قَالَ رَبُّ السَّمَاوَاتِ وَالْأَرْضِ وَمَا بَيْنَهُمَا

((Musa) said: "The Lord of the heavens and the earth, and all that is between them...") meaning, the Creator, Sovereign and Controller of all that, their God Who has no partner or associate. He is the One Who has created all things. He knows the higher realms and the heavenly bodies that are in them, both those that are stationary and those that move and shine brightly. He knows the lower realms and what is in them; the oceans, continents, mountains, trees, animals, plants and fruits. He knows what is in between the two realms; the winds, birds, and whatever is in the air. All of them are servants to Him, submitting and humbling themselves before Him.

إِن كُنتُم مُّوقِنِينَ

(if you seek to be convinced with certainty.) means, if you have believing hearts and clear insight. At this, Fir'awn turned to the chiefs and leaders of his state around him, and said to them – mockingly expressing his disbelief in Musa:

أَلَا تَسْتَمِعُونَ

("Do you not hear?") meaning, 'are you not amazed by what this man is claiming – that you have another god other than me' Musa said to them:

رَبُّكُمْ وَرَبُّ آبَائِكُمُ الْأَوَّلِينَ

(Your Lord and the Lord of your ancient fathers!) meaning, the One Who created you and your forefathers, those who came before Fir'awn and his time.

قَالَ

(He said) that is, Fir'awn said:

إِنَّ رَسُولَكُمُ الَّذِي أُرْسِلَ إِلَيْكُمْ لَمَجْنُونٌ

(Verily, your Messenger who has been sent to you is a madman!) meaning, there is no sense in his claim that there is any god other than me!'

قَالَ 

((Musa) said) – to those in whose hearts Fir'awn had planted doubts:

رَبُّ الْمَشْرِقِ وَالْمَغْرِبِ وَمَا بَيْنَهُمَا ۖ إِن كُنتُمْ تَعْقِلُونَ

(Lord of the east and the west, and all that is between them, if you did but understand!)

He is the One Who made the east the place where the heavenly bodies rise, and made the west the place where they set; this is the system to which He has subjugated all the heavenly bodies, stationary and moving. If what Fir'awn claims is true, that he is your lord and your god, then let him turn things around so that the heavenly bodies set in the east and rise in the west.' This is similar to the Ayah,

الَّذِي حَاجَّ إِبْرَاهِيمَ فِي رَبِّهِ أَنْ آتَاهُ اللَّهُ الْمُلْكَ إِذْ قَالَ إِبْرَاهِيمُ رَبِّيَ الَّذِي يُحْيِي وَيُمِيتُ قَالَ أَنَا أُحْيِي وَأُمِيتُ ۖ قَالَ إِبْرَاهِيمُ فَإِنَّ اللَّهَ يَأْتِي بِالشَّمْسِ مِنَ الْمَشْرِقِ فَأْتِ بِهَا مِنَ الْمَغْرِبِ

(who disputed with Ibrahim about his Lord, because Allah had given him the kingdom? When Ibrahim said: "My Lord is He Who gives life and causes death." He said, "I give life and cause death." Ibrahim said, "Verily, Allah brings the sun from the east. So cause it to rise from the west.")(2:258)

So when Fir'awn was defeated in debate, he resorted to the use of his force and power, believing that this would be effective in dealing with Musa, peace be upon him, so he said, as Allah tells us: