The Quran proofs itself that it is the book of God

That it’s miraculous. Let me explain, the Quran is neither prose nor poetry; rather, it’s a unique form never done before. No one can produce anything like it. Actually God challenged all humankind to produce a single chapter like those in the Quran and none managed to even come close.

To make the picture clearer, the shortest chapter in the Quran is like a half line, here it is :
(إنا أعطيناك الكوثر ۞ فصلي لربك وأنحر ۞ إن شانئك هو الأبتر)

This half line, no one could produce something even close to it. This chapter contains all Arabic language in it, you will see how!

You can stop reading now, but i will add more details about this Chapter to show how miraculous it is :

1- First Verse from the three, contains 10 non-repeated letters :ا--ن--ع--ط--ي--ك--ل--و--ث--ر
Second Verse from the three, also contains 10 non-repeated letters:ف--ص--ل--ر--ب--ك--و--ا--ن--ح
Third Verse from the three, also contains 10 non-repeated letters:ا--ن--ش-ك--ه--و--ل--ب--ت--ر
There are also across the chapter 10 letters which were repeated twice : ع--ط--ي--ث--ف--ص--ح--ش--ه--ت
Remember, Muhammed (peace be upon him) was illiterate!!

2- How the chapter contains the Arabic language? There are many types of pronouns in Arabic (different than English). Linguists divide them according to many categories :

Obvious or Hidden? both exist in this chapter : Obvious in أعطيناك and Hidden in انحر
Connected or disconnected? both exist in this chapter : Connected in أعطيناك and Disconnected in هو الأبتر
Pronouns with the three grammatical cases: The three cases exist :
Nominative in : نا in أعطيناك
Accusative in : ك in أعطيناك
Genitive in : ك in ربك
Singular and plural pronouns? Both exist :
Singular in : ك in أعطيناك
Plural in : نا in إنا
3 persons pronouns? all exist :
1st person pronoun : نا in إنا
2nd person pronoun : ك in أعطيناك
3rd person pronoun : هو
Then comes the verbs (Also different than English)
There are different types of verbs in Arabic linguistics, and they are classified according to certain aspects. So first classification is of the position of vowels in the verb (i.e. at the end or no vowels at all) : The whole chapter contains only three verbs .....أعطي) (صلى) و(نحر.., yet they contain all types:

Sahih verb “no vowels at all” : نحر
Mu’tal Verb “vowel at the end” : صلي
Mujarrad verb “all letters are necessary” : نحر
Mazeed verb “you can omit a letter or more” : أعطي
Mazeed verbs are formed either by adding a letter or by doubling a letter. Both exist :
Adding a letter : أعطي
Doubling a letter : صلي
Transitive or intransitive verbs? All exist
Transitive verbs in grammar means verbs that require one or more objects, whereas intransitive ones don’t require an object.
Intransitive verb : صلي
Transitive verb with one object : أنحر
Transitive verb with two objects : أعطي
Then comes nouns; three words referred to God Almighty with the three grammatical cases:
Accusative in : نا in إنا
Nominative in : نا in أعطيناك
Genitive in : رب in ربك
Three words (ك) referred to the Prophet (peace be upon him) :
ك in شانئك
ك in أعطيناك
ك in ربك
Three words referred to the Prophet (peace be upon him) with the three grammatical cases:
Accusative in : ك in أعطيناك
Nominative in : the hidden pronoun with صل
Genitive in : ك in ربك
Now let’s see the sentences : Sentences are classified according to many categories (Not like English) so one of these categories is wheter they tell something جملة خبرية “Jumlah Khabareyyah” (i.e. i bought a book) or literary style جملة انشائية “Jumlah Insha’yyah” like imperative..etc (i.e. beware of dogs). Both exist :
Jumlah Khabareyyah : إنا أعطيناك الكوثر
Jumlah Insha’yyah : فصل لربك وأنحر
Verbal or noun phrase? Both exist:
Verbal phrase : فصل لربك
Noun pharse : إن شانئك هو الأبتر
Simple or compound phrase? Both exist :
Simple : فصل لربك
Compound : إن شانئك هو الأبتر
Phrases Connectivity? both exist :
Connection “Wasl” : between first verse and second verse
Disconnection “Fasl”: between second verse and third verse