Reading later parts of the Qur’aan before earlier parts is called Tankees (inversion). There are different types of Tankees:

Tankees al-Huroof (inversion of letters)

Tankees al-Kalimaat (inversion of words)

Tankees al-Aayat (inversion of verses)

Tankees al-Suwar (inversion of Soorahs)

Tankees al-Huroof (inversion of letters) means putting a later letter before a previous letter in one word, for example, instead of “Rabb” one reads “Barr”

Undoubtedly this is haraam, and invalidates a person's prayer, because it changes the Qur’aan from the way in which it was spoken by Allaah, and usually alters the meaning in a drastic manner.

(Al-Sharh al-Mumti’ by Ibn ‘Uthaymeen, 3/110)

Tankees al-Kalimaat (inversion of words) means putting a later word before a previous word, for example, instead of “Qul huwa Allaahu ahad”, one reads “Ahad Allaah huwa qul”!

This also is undoubtedly haraam, because it changes the Qur’aan from the way in which it was spoken by Allaah.

(Al-Sharh al-Mumti’, 3/110)

Tankees al-Aayat (inversion of verses) means reciting a later aayah before a previous aayah, for example, reciting “min sharr il-waswaas il-khannaas” before “ilaah il-naas”!

Concerning this, al-Qaadi ‘Ayyaad (may Allaah have mercy on him) said:

There is no dispute concerning the order of the aayahs in each soorah. This is something which is Tawqeefi, i.e., based on revelation [and is not open to ijtihaad], and the order is that which now appears in the Mus-haf, and this is how the ummah transmitted it from the Prophet  (peace and blessings of Allaah be upon him).

(Sharh al-Nawawi, 6/62. This was also the view of Ibn al-‘Arabi, as stated in al-Fath, 2/257).

Shaykh Ibn ‘Uthaymeen said:

Tankees al-aayaat (inverting verses) is also haraam according to the most correct view, because the order of the aayahs is tawqeefi (something which is based on revelation [and not open to ijtihaad]). The meaning of “tawqeefi” is that it was dictated by the order of the Messenger  (peace and blessings of Allaah be upon him).

(al-Sharh al-Mumti’, 3/110).

Tankees al-Suwar (inversion of Soorahs) means, reciting later soorahs before earlier ones, for example, reciting Aal ‘Imraan before al-Baqarah.

The ruling on this:

Those scholars who say that the order of soorahs is not tawqeefi do not see anything wrong with this.

Those who think that it is tawqeefi or that the consensus of the Sahaabah on the order of soorahs is evidence, do not think that it is permissible.

The correct view:

Is that the order of soorahs is not tawqeefi; it is the result of ijtihaad on the part of some of the Sahaabah.

There was no ijmaa’ (consensus) among the Sahaabah on the order of soorahs; the order in the Mus-haf of ‘Abd-Allaah ibn Mas’ood – for example – is different from that in the Mushafs of others.

In the Sunnah there is evidence that supports the view that it is permissible:

(A) Hudhayfah said: I prayed with the Prophet  (peace and blessings of Allaah be upon him) one night, and he started to recite al-Baqarah. I thought, he will do rukoo’ when he reaches one hundred aayaat, but he kept going. I thought, he will complete it in one rak’ah, but he kept going. I thought, he will do rukoo’ now, but he started to recite al-Nisaa’, and he recited all of it, then he started to recite Aal ‘Imraan and recited all of it… (Narrated by Muslim, 772).

The evidence in this hadeeth is that he recited al-Nisaa’ then Aal ‘Imraan.

The Prophet  (peace and blessings of Allaah be upon him) and the ummah after him in all ages regarded it as permissible to differ from the order of soorahs in prayer, and when studying and teaching.

He said: with regard to the view of those scholars who say that (the order of soorahs) was set by the Prophet  (peace and blessings of Allaah be upon him) and that he put them in the same order as appears in the Mus-haf of ‘Uthmaan – and that the different orders came about before they heard of his ruling and his final review of the Qur’aan with Jibreel – they interpret the fact that he  (peace and blessings of Allaah be upon him) recited al-Nisaa’ first and then Aal ‘Imraan as meaning that this happened before the final ruling was dictated, and these two soorahs appear in this order in the Mus-haf of Ubayy.

He said: there is no dispute concerning the fact that a person who is praying may recite in the second rak’ah a soorah which comes before the soorah which he recited in the first rak’ah; but it is makrooh to do this in one rak’ah, or when reciting Qur’aan outside of salaah.

He said: but some of them permitted this.

The prohibition of the Salaf against reading the Qur’aan backwards is interpreted as referring to those who read from the end of a soorah to the beginning.

He said: there is no dispute concerning the fact that the order of aayaat in each soorah is based on revelation from Allaah and is as it now appears in the Mus-haf and as it was transmitted by the ummah from the Prophet  (peace and blessings of Allaah be upon him).

(End of the comments of al-Qaadi ‘Ayyaad). And Allaah knows best.

(Sharh Muslim, 6/61, 62).

The evidence in this report is the fact that the man recited Soorat al-Ikhlaas in his prayer before any other soorah that comes before it (in the Mus-haf), and the Prophet  (peace and blessings of Allaah be upon him) approved of that.

(C) This is the action of ‘Umar (may Allaah be pleased with him).