Bismillāh-ir-Rahmān-ir-Rahīm, Wal-Hamdu lillaāhi Rabb-il-’Ālamīn. Was-Salātu Was-Salāmu ‘alā Sayyidinā Muhammadin Khātimin-Nabiyyīna wa Imām-il-Mursalīn.
Firstly, the question itself is invalid. The word ‘where’ means: in, at or to what place or position. In other words, it refers to a place, directionality, location etc. So what the questioner is really asking is, “What is the location of Allāh?” This is an invalid question because Allāh is free from place directionality and is not contingent to time and space.
Those who say “Allāh is above the Heavens, above the throne (literally)” or say “Allāh is everywhere (literally)” may fall out the fold of Islām. Here’s why:
The first statement limits Allāh to a place, which implies that He is a body or a particle; as directionality and space is only applicable to bodies and particles. This is anthropomorphism and you’ll see all the books of ‘Aqīdah warned us against such belief. When it is mentioned in the Qur’ān that Allāh is above the Heavens and the Earth, and Above His throne, that’s not his physical place, but rather He is above all of His creation in rank and status, and free from all needs and imperfections. If He was “on” something, that’d mean He’s being carried. If He was “in” something, that’d mean He’s being contained. And if He was “from” something, that’d mean He was created. All of these are imperfections and Allah – Exalted beyond measures – is Perfect and free from all imperfections.
The second statement is pantheism. Because those who say it, say it in response to the first statement, because first implies Allāh has a limit and by teaching the second it’d imply that He has no limit. This is pantheism, and not the creed of Ahlus Sunnah wal-Jamā’ah (The People of the Prophetic Way and Majority of Scholars). However, if someone said Allāh is everywhere with His Knowledge, then that’s something we affirm, but if someone asks “Where is Allah” and you say “Everywhere”, that’s heresy.
Sayyidunā ‘Alī (Allāh be pleased with him) said:
“Allāh existed when there was no place, and He is now where He has always been [i.e. without place].”
(Al-Farq bayna al-Firāq, Pg. 333)
Imām Abū Hanīfah (Allāh be pleased with him) said:
“If it is asked, ‘Where is Allāh?’ It will be said to him that Allāh, Most High, existed when there was no place, before creating the creation. And Allāh, Most High, existed when there was no ‘where’, no creation, nothing; and He is the Creator of everything.”
(Al-Fiqh al-Absat, P: 21)
Ibn Hajar al-‘Asqalānī (Allāh be pleased with him) said:
“Some of the Mu`tazila (Heretics) have claimed that Allāh was everywhere on the basis of the hadīth “If one of you stands in prayer, let him not spit in front of him for Allāh is in front of him.” This is evident ignorance, because the hadīth then states that he should spit under his foot, which invalidates their principle. The hadith also constitutes a refutation of those who say that Allāh is on the Throne *in person*.”
Sulaymān ibn ‘Abdul Wahhāb (Allāh be pleased with him) said:
“Whoever believes or says: Allāh is in person (bi dhatihi) in every place, or in one place: he is a disbeliever (kāfir). It is obligatory to declare that Allāh is distinct from His creation, established over His throne without modality or likeness or examplarity. Allāh was and there was no place, then He created place and He is exalted as He was before He created place.”