Al-Ash'arî said in his book al-Ibânah fî Usûl'id Diyânah in the chapter on Istiwâ, "If someone says: What do you say regarding Istiwâ? It is said to him: We say: Verily, Allâh has done Istiwâ above His throne, as He said,﴿الرَّحْمَنُ عَلَى الْعَرْشِ اسْتَوَى﴾
"Ar-Rahmân did Istiwâ above the Throne." (Tâ-Hâ, 20/5)
He said,﴿إِلَيْهِ يَصْعَدُ الْكَلِمُ الطَّيِّبُ﴾
"Towards Him ascends the pure word." (Fâtir, 35/10)
And He said,﴿بَلْ رَفَعَهُ اللهُ إِلَيْهِ﴾
"Rather, Allâh raised him to Himself." (an-Nisâ, 4/158)
He said while narrating from Pharoah,﴿يَاهَامَانُ ابْنِ لِي صَرْحًا لَعَلِّي أَبْلُغُ الْأَسْبَابَ ۞ أَسْبَابَ السَّمَاوَاتِ فَأَطَّلِعَ إِلَى إِلَهِ مُوسَى وَإِنِّي لَأَظُنُّهُ كَاذِبًا﴾
"O Hâmân! Construct for me a tower that I might reach the ways -the ways into the heavens- so that I may look at the deity of Mûsa; but indeed, I think he is a liar." (Ghâfir, 40/36-37)
He belied Mûsâ Alayh'is Salâm in his statement, "Verily, Allâh is in the heavens."
Allâh Azza wa Jalla said,﴿أَأَمِنْتُمْ مَنْ فِي السَّمَاءِ أَنْ يَخْسِفَ بِكُمُ الْأَرْضَ فَإِذَا هِيَ تَمُورُ﴾
"Do you feel secure that He, Who is in the heaven (Allâh), would not cause the earth to swallow you, and suddenly it would sway?" (al-Mulk, 67/16)
Above the heavens is the throne. Since the throne is above the heavens, Allâh said,﴿أَأَمِنْتُمْ مَنْ فِي السَّمَاءِ﴾
"Do you feel secure from He, Who is in the heaven (Allâh)?" (al-Mulk, 67/16)
This is because Allâh has done Istiwâ above the Arsh which is above the heavens. Everything that is above is the Samâ, thus the Arsh is the highest heaven. When Allâh said,﴿أَأَمِنْتُمْ مَنْ فِي السَّمَاءِ﴾
"Do you feel secure from He, Who is in the heaven (Allâh)?" (al-Mulk, 67/16)
He did not intend the entirety of the heavens; He only intended the Arsh which is the highest of the heavens."235
He said, "We see that when all Muslims supplicate, they raise their hands towards the heaven. This is because Allâh has done Istiwâ above His throne which is above the heavens. If Allâh was not upon His Arsh, they would not raise their hands towards the Arsh.
Some of the Mu'tazilah, Jahmiyyah, and Harûriyyah said, "The meaning of Istiwâ is overcome, acquired, and overwhelmed it and that Allâhu Taâlâ is in everyplace. They deny that Allâh is upon His Arsh. They were of the opinion that Istiwâ is power. If it was as they said, there would be no difference between the Arsh and the seventh earth. This is because He is powerful over everything. Again, if He had done Istiwâ above His Arsh in the meaning of overcoming, it would be permissible to say, "He has done Istiwâ above everything." According to everyone who is Muslim, it is impermissible to say, "Allâh has done Istiwâ above the lavatories and toilets." Thus, doing Istiwâ above the Arsh meaning overcoming it is invalid."236
He then mentioned other evidences from the Book, Sunnah, and intellect (ration).
The book al-Ibânah is among the most popular works of Abu'l Hasan. Hâfidh Ibnu Asâkir popularised it and relied upon it, and Imâm Muhyi'd Dîn an-Nawawî copied it with his own handwriting.
235- Al-Ash'arî, al-Ibânah fî Usûl'id Diyânah, Dâr'ul Fadhîlah, p. 405-408.
236- Al-Ash'arî, al-Ibânah fî Usûl'id Diyânah, Dâr'ul Fadhîlah, p. 409-413.