Ruling on describing the Quran as the eternal word of Allah
Question

What is the ruling on describing the Quran as the eternal word of Allah?
Praise be to Allah.Firstly:
The Noble Quran is the word of Allah, may He be exalted, its words, letters and meanings. It originated from Him and will return to Him. It was uttered by Allah, may He be exalted, and heard from Him by Jibreel (peace be upon  him), who brought it down to Muhammad (blessings and peace of Allah be upon him). Allah, may He be glorified, says (interpretation of the meaning):
“That (this) is indeed an honourable recital (the Noble Quran).
In a Book well-guarded (with Allah in the heaven i.e. Al-Lauh Al-Mahfooz).
Which (that Book with Allah) none can touch but the purified (i.e. the angels)”
[al-Waaqi‘ah 56:77-80]
“Alif Laam Meem. (These letters are one of the miracles of the Quran, and none but Allah (Alone) knows their meanings.)
The revelation of the Book (this Quran) is from the Lord of the Alameen (mankind, jinns and all that exists) in which there is no doubt”
[as-Sajdah 32:1,2]
“The revelation of this Book (the Quran) is from Allah, the All-Mighty, the All-Wise”
[az-Zumar 39:1].
The Quran comes under the heading of His words or speech, which is one of His attributes. Therefore whoever says that it is created is a disbeliever. This is the belief of Ahl as-Sunnah wa’l-Jamaa‘ah, in contrast to the beliefs of deviant groups.
At-Tahhaawi (may Allah have mercy on him) said in his famous book al-‘Aqeedah:
The Quran is the word of Allah, which originated from Him – without discussing how it was spoken. He sent it down to His Messenger by means of revelation (wahy). The believers bear witness to its revelation. They are certain that it is the actual words of Allah. It is not created like the words of human beings. Whoever hears it and thinks that it is the words of human beings is a disbeliever; Allah has condemned him, criticised him and warned him of hellfire as He, may He be exalted, says (interpretation of the meaning): “I will cast him into Hell-fire” [al-Muddaththir 74:26]. Because Allah has given the warning of hellfire to those who say “ ‘This is nothing but the word of a human being’” [al-Muddaththir 74:25], we know with certainty that it is the words of the Creator of human beings, and is not like the words of human beings. End quote. 
Ibn Qudaamah (may Allah have mercy on him) said:
Part of the speech of Allah, may He be glorified, is the Noble Quran, which is the clear Book of Allah, His strong rope and straight path, the revelation of the Lord of the Worlds, which was brought down by the Trustworthy Spirit (ar-Rooh al-Ameen, i.e., Jibreel) to the heart of the leader of the Messengers, in a clear Arabic tongue, revealed not created. It originated from Him and will return to Him. It consists of clear soorahs and clear verses, letters and words. Whoever recites it clearly and correctly will have for each letter ten hasanaat. It has a beginning and an end, and consists of parts (ajza’) and smaller sections. It is recited on people’s lips and is memorised in their hearts, listened to and written in the Mus-hafs. It has both clear and ambiguous verses, that which abrogates and that which is abrogated, general and specific words, commands and prohibitions.
“Falsehood cannot come to it from before it or behind it (it is) sent down by the All-Wise, Worthy of all praise (Allah )”
[Fussilat 41:42]
“Say: ‘If the mankind and the jinns were together to produce the like of this Quran, they could not produce the like thereof, even if they helped one another’”
[al-Isra’ 17:88].
It is this Arabic book of which those who disbelieve say: “ ‘We will never believe in this Quran’” [Saba’ 34:31] and some of them said: “ ‘This is nothing but the word of a human being’” [al-Muddaththir 74:25], so Allah, may He be glorified, said: “I will cast him into Hell-fire” [al-Muddaththir 74:26].
There is no difference of opinion among the Muslims that whoever rejects a soorah, verse, word or letter of the Quran on which there is agreement is a disbeliever, and this offers definitive proof that it consists of letters. End quote.
Lam‘at al-I‘tiqaad (p. 22-28)
What is meant by the words of Ahl as-Sunnah, “it originated from Him”, is that Allah, may He be exalted, uttered it, so its original appearance and its beginning was from Allah, may He be exalted.
What is meant by their words, “it will return to Him”, is that it will be taken away from people’s hearts and from the Mus-hafs at the end of time, and not one verse of it will remain in people’s hearts or in the Mus-hafs, as is mentioned in a number of reports.
Al-Haafiz Diya’ ad-Deen al-Maqdisi (d. 643) wrote an essay on this topic entitled Ikhtisaas al-Quran bi’l-Awd ila ar-Rahmaan.
The innovators have many other views that are contrary to what is indicated by sheer common sense and the soundly narrated texts concerning this matter, which you may check and learn the scholars’ refutations thereof in the books of Ahl as-Sunnah that deal with this topic, including books that deal specifically with refutation of the innovators’ views on the divine attribute of speech, such as al-Burhaan fi Mas’alat al-Quran and Hikaayat al-Munaazarah fi’l-Quran, both of which are by Muwaffaq ad-Deen Ibn Qudaamah, the author of al-Mughni (may Allah have mercy on him). Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) also wrote several books and essays having to do with the issue of the divine attribute of speech. See vol. 12 of his Majmoo‘ al-Fataawa; one of his most important books on that topic is at-Tis‘eeniyyah, which is a refutation of the Ash‘aris’ innovated views concerning the divine attribute of speech, based on approximately ninety points.
With regard to contemporary books, this issue has been dealt with specifically in a book by Shaykh ‘Abdullah al-Judayyi‘ entitled al-‘Aqeedah as-Salafiyyah fi Kalaam Rabb al-Bariyyah, which is a useful book on this topic.
Secondly:
Describing the Quran as eternal or describing the words of Allah, may He be exalted, as eternal, may be interpreted in two ways:
The first interpretation is:
that it is not created, as mentioned above, and that attribute of speech, in the case of Allah, may He be exalted, is eternal, for He speaks whenever He wills, however He wills, to whiomever of His slaves He wills. This is sound and correct, and this is what is meant by those of Ahl as-Sunnah who give the description of eternal to the Quran or to the divine attribute of speech in general.
Among those who used this description was Abu’l-Qaasim al-Laalkaa’i in his book Sharh Usool I‘tiqaad Ahl as-Sunnah wa’l-Jamaa‘ah.
He said (2/224):
What we may understand from various reports narrated from the Prophet (blessings and peace of Allah be upon him) is that the Quran is one of the eternal attributes of Allah.
Then he said (2/227):
There are reports of consensus among the Sahaabah that the Quran is not created.
Another scholar who used this description was Ibn Qudaamah (may Allah have mercy on him) in Lam‘at al-I‘tiqaad, where he said (15):
One of the attributes of Allah, may He be exalted, is that of speech, and He speaks eternal words that are heard from Him by whoever He wills of His creation. Moosa (peace be upon him) heard from Him without any intermediary. Jibreel (peace be upon him) also heard from Him, as did other angels and Messengers to whom He gave leave. Allah, may He be exalted, will speak to the believers in the hereafter and they will speak to Him; He will give them permission to visit Him. Allah, may He be exalted, says (interpretation of the meaning):
“and to Moosa (Moses) Allah spoke directly”
[al-Nisa’ 4:164]
“(Allah) said: ‘O Moosa (Moses) I have chosen you above men by My Messages, and by My speaking (to you)’”
[al-A‘raaf 7:144]
“to some of them [the Messengers] Allah spoke (directly)”
[al-Baqarah 2:253]
“It is not given to any human being that Allah should speak to him unless (it be) by Inspiration, or from behind a veil”
[ash-Shoora 42:51]
“And when he came to it (the fire), he was called by name: ‘O Moosa (Moses)!
‘Verily! I am your Lord! So take off your shoes, you are in the sacred valley, Tuwa’”
[Ta-Ha 20:11-12]
“ ‘Verily! I am Allah! La ilaha illa Ana (none has the right to be worshipped but I), so worship Me’”
[Ta-Ha 20:14].
It is not possible that anyone could have said these words except Allah… End quote.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
The early generations said: The Quran is the word of Allah that was revealed and is not created. And they said that He speaks when He wills. Then they explained that the words of Allah are eternal, meaning that the divine attribute of speech is eternal.
Not one of them said that any particular words of His are eternal, and not one of them said that the Quran is eternal.
Rather they said that it is the word of Allah; it was revealed and is not created.
As Allah uttered the Quran by His will, the Quran is His word, and it was revealed from Him and not created, yet despite that it is not eternal as Allah is eternal, even though Allah has the attribute of speech and speaks whenever He wills. So the attribute of speech is eternal (and part of His essence).
Whoever understands the words of the early generations and sees the subtle differences between the various statements will no longer have any doubt about these difficult issues that many people are confused about.
End quote from Majmoo‘ al-Fataawa (12/54)
And he (may Allah have mercy on him) also said:
The word of Allah is what Allah uttered Himself and spoke by His will and power. It is not something created that is distinct from Him; rather it exists with Him in His essence, even though He uttered it by His might and will, and it does not exist independently of His might and will.
The early generations said: Allah, may He be exalted, speaks when He wills. If it is said that the words of Allah are eternal, in the sense that speech is His eternal attribute and in the sense that His words are not created, and in the sense that His words are not a concept that exists in His essence – rather Allah speaks whenever He wills – then this is correct.
Not one of the early generations said that these particular words are eternal. Rather they used to say: the Quran is the word of Allah, revealed and not created; it originated with Him and will return to Him.
Not one of them said that the Quran is eternal, and they did not say that His words are a concept that exists in His essence. And they did not say that the letters of the Quran, or its letters and sounds, are eternal and exist in the essence of Allah, even though the letters themselves may be uttered by Allah whenever He wills. Rather they said that the letters of the Quran are not created, and they denounced those who said that Allah created the letters.
End quote from al-Fataawa (12/566-567)
The second interpretation is:
that the Quran is a concept, or a concept and letters, that Allah uttered from eternity, then never uttered it after that. This is one of the innovations of the Ash‘aris and those who agreed with them among the Islamic philosophers (ahl al-kalaam), by which they sought to avoid falling into the innovation of the Mu‘tazilah and Jahamis who held the view that the Quran was created.
Whoever says that the Quran is eternal, meaning it literally, his understanding is flawed. Moreover, the way they presented this idea is very general and there is no report from the early generations to support it.
Because of this false meaning that may be indicated by this general wording, and because it is not reported or found in any report from the early generations, what we think most likely to be the case is that the word eternal should not be used to describe the Quran. Rather we should say concerning it what the early generations said: the Quran is the word of Allah, not created.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
The followers of the salaf (early generations) say: The word of Allah is eternal, that is: He has the attribute of speech and speaks whenever He wills. They do not say that a specific word is eternal, such as His call to Moosa and the like.
But these people [meaning the Ash‘aris and those who agreed with them] believe that the Quran and all the words of Allah are eternal, and that Allah does not speak by His will. Then they differed:
Some of them say that what is eternal is one concept, which is all the meanings of the Torah, Gospel and Quran; and that if the Torah is expressed in Arabic, it becomes Quran, and if the Quran is expressed in Hebrew, it becomes Torah. They said: The Arabic Quran was not spoken by Allah; rather what happened was that either He created it in some physical entities, or it was produced by Jibreel or Muhammad, so it is the words of that Messenger, which is a reflection of that one concept that exists in the divine essence, which is all the meanings of the words.
Some of them said: rather the eternal Quran is letters, or letters and sounds, which are eternal and existed in the divine essence from eternity to eternity.… When Allah spoke to Moosa or to the angels, or when He will speak to people on the Day of Resurrection, He is not speaking words that He utters by His will when He speaks them; rather He creates some understanding in (the human or angel) so that he may understand those eternal words that are part of the essence of Allah from eternity to eternity.
According to them, He was and is still saying (interpretation of the meaning): “O Adam! Dwell you and your wife in Paradise” [al-Baqarah 2:35], “O Nooh (Noah)! Come down (from the ship) with peace from Us and blessings on you” [Hood 11:48], “O Iblees (Satan)! What prevents you from prostrating yourself to one whom I have created with Both My Hands” [Saad 38:75] and so on….
And he [Ibn Taymiyah] examined these views further in several other places.
The point we are trying to prove is that no one can transmit either of these two views from any of the early generations, meaning the Sahaabah and Taabi‘een, and those who followed them in guidance, and all the imams (leading scholars) of the Muslims who are known for their knowledge and religious commitment, who are well respected by the ummah, whether at the time of Ahmad ibn Hanbal, or at the time of ash-Shaafa‘i, or at the time of Abu Haneefah, or before that. The first one to introduce this idea was Abu Muhammad ‘Abdullah ibn Sa‘eed ibn Kilaab.
Al-Fataawa (17/85)
Based on that, whoever says that the Quran is eternal, or the word of Allah is eternal, in the sense of the fist interpretation, which is that the Quran and all the words of Allah are revelation from Him, and not created, yet it is subject to His will, this is valid, although it is preferable and more prudent to limit it to the wording and phrases narrated from the early generations, that avoid being too general and being subject to false interpretations. 
But if he means the second interpretation, which says that Allah’s words are not subject to His will, then this is false, and the words used are also innovation (bid‘ah).
See also: Minhaaj as-Sunnah an-Nabawiyyah by Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) – (5/419-421) 
And Allah knows best.