And thou wast not (able) to recite a Book before this (Book came),
nor art thou (able) to transcribe it with thy right hand: In that case, indeed, would the talkers of vanities have doubted
Quran 29:38
It is clearly showing that the doubters who might have claimed he was copying from previous scriptures have no chance, but there must be more wisdom in this as will be seen below.
When the treaty of Hudaybiya was written down, ali wrote, in the name of Allah, most gracious most merciful, this is a treaty between Muhammad the messenger of God and .....
The envoy from the other side began reading and said,
We don't know what most gracious most merciful is so write: in your name o Allah,
The prophet told ali to change it, so he did,
Then the envoy continued reading and told them to change messenger of God to Muhammad the son of Abdullah, the prophet said, regardless of wether you accept it or not I am the messenger of God, ali change it, ali refused saying he couldn't get himself to do that (the other side was trying to cause a bust-up and the prophet needed the treaty) so the prophet asked, where is it written, he was shown and he crossed it out himself,
This happened in front of his most important companions (hundreds) that showed even a sentence was impossible.
Yet he took over leadership if the whole of the Arabian peninsula and even those arrogant envoy's had co come and humbly apologise, right now almost a quarter of the worlds population is behind him and growing.
Including doctors, teachers, engineers, professors with the highest degrees.
When Gabriel first appeared to him at the mount,
He was ordered:
iqra - READ
And he replied: Ma Ana Bi Qarin - I AM NOT LEARNED
Iqra is the first word revealed - Sura alaq
From the Quran we see this mentioned along with the previous scriptures:
"Those who follow the messenger, the unlettered Prophet,
whom they find mentioned in their own (scriptures),
- in the Torah and the Gospel;
- for he commands them what is just and forbids them what is evil; he allows them as lawful what is good (and pure) and prohibits them from what is bad (and impure); He releases them from their heavy burdens and from the yokes that are upon them. So it is those who believe in him, honour him, help him, and follow the light which is sent down with him,- it is they who will prosper."
Quran 7.157
So where is this?
These verses are on the same page in he bible:
New American Standard Bible (©1995)
Then the book will be given to the one who is illiterate, saying, "Please read this."
And he will say, "I cannot read."
King James Bible
And the book is delivered to him that is not learned, saying,
Read this, I pray thee:
and he saith, I am not learned.
13Wherefore the Lord said, Forasmuch as this people draw near me with their mouth,
and with their lips do honour me, but have removed their heart far from me,
and their fear toward me is taught by the precept of men:
14Therefore, behold, I will proceed to do a marvellous work among this people,
even a marvellous work and a wonder:
for the wisdom of their wise men shall perish,
and the understanding of their prudent men shall be hid.
Isaiah 29:12-14
It was revealed a few verses at a time in different cities over the course of 23 years. From age 40 to age 63.
On the same page just a little earlier you'll find a description:
10For precept must be upon precept,cprecept upon precept;
line upon line, line upon line;
here a little, and there a little:
11For with stammering lips and another tongue will he speak to this people.
12To whom he said, This is the rest wherewith ye may cause the weary to rest; and this is the refreshing: yet they would not hear.
13But the word of the LORD was unto them precept upon precept, precept upon precept;
line upon line, line upon line;
here a little, and there a little;
that they might go, and fall backward, and be broken, and snared, and taken.
14Wherefore hear the word of the LORD, ye scornful men, that rule this people which is in Jerusalem.
Isaiah 28:10-14
It also spoke of REST (above)
No new law was revealed after Moses (pbuh) even Jesus (pbuh) followed the law of Moses (pbuh) yet one was prophesied after him:
Hearken unto me, my people; and give ear unto me, O my nation:
for a law shall proceed from me, and I will make my judgment to rest for a light of the people.
Isaiah 51:4
Regarding your question on trust in writing down,
The word Quran means "recital" although it is recorded in a book,
The main objective is to be able to recite and comprehend it.
The whole book was memorised and recited by the prophet and his companions constantly,
King James Bible
But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
Jeremiah 31:33
And I will sow her unto me in the earth;
and I will have mercy upon her that had not obtained mercy;
and I will say to them which were not my people, Thou art my people;
and they shall say, Thou art my God.
Hosea 2:23
14And Abraham rose up early in the morning, and took bread, and a bottle of water, and gave it unto Hagar, putting it on her shoulder, and the child, and sent her away: and she departed, and wandered in the wilderness of Beersheba.
15And the water was spent in the bottle, and she cast the child under one of the shrubs. 16And she went, and sat her down over against him a good way off, as it were a bowshot: for she said, Let me not see the death of the child. And she sat over against him, and lift up her voice, and wept. 17And God heard the voice of the lad; and the angel of God called to Hagar out of heaven, and said unto her, What aileth thee, Hagar? fear not; for God hath heard the voice of the lad where he is. 18Arise, lift up the lad, and hold him in thine hand; for I will make him a great nation. 19And God opened her eyes, and she saw a well of water; and she went, and filled the bottle with water, and gave the lad drink.
20And God was with the lad; and he grew, and dwelt in the wilderness, and became an archer.
21And he dwelt in the wilderness of Paran:
and his mother took him a wife out of the land of Egypt.
Genesis 21
(Sarah was barren so she had given hajar to abraham to bear a child
Hajar was a servant girl.)
The Muslim nation is around 1.5billion
1Sing, O barren, thou that didst not bear; break forth into singing, and cry aloud, thou that didst not travail with child: for more are the children of the desolate than the children of the married wife, saith the LORD.
2Enlarge the place of thy tent, and let them stretch forth the curtains of thine habitations: spare not, lengthen thy cords, and strengthen thy stakes;
3For thou shalt break forth on the right hand and on the left; and thy seed shall inherit the Gentiles, and make the desolate cities to be inhabited......
....
6For the LORD hath called thee as a woman forsaken and grieved in spirit, and a wife of youth, when thou wast refused, saith thy God.
7For a small moment have I forsaken thee; but with great mercies will I gather thee.
Isaiah 54
It keeps speaking of wisdom of the wise and prudent being hidden,
Now we know that the Arabs were a rowdy illiterate lot who no king bothered to even conquer as a whole:
King James Bible
They have moved me to jealousy with that which is not God; they have provoked me to anger with their vanities: and I will move them to jealousy with those which are not a people; I will provoke them to anger with a foolish nation.
Dueteronomy 32:21
33Hear another parable: There was a certain householder, which planted a vineyard, and hedged it round about, and digged a winepress in it, and built a tower, and let it out to husbandmen, and went into a far country: 34And when the time of the fruit drew near, he sent his servants to the husbandmen, that they might receive the fruits of it. 35And the husbandmen took his servants, and beat one, and killed another, and stoned another. 36Again, he sent other servants more than the first: and they did unto them likewise. 37But last of all he sent unto them his son, saying, They will reverence my son. 38But when the husbandmen saw the son, they said among themselves, This is the heir; come, let us kill him, and let us seize on his inheritance. 39And they caught him, and cast him out of the vineyard, and slew him. 40When the lord therefore of the vineyard cometh, what will he do unto those husbandmen? 41They say unto him, He will miserably destroy those wicked men, and will let out his vineyard unto other husbandmen, which shall render him the fruits in their seasons.
42Jesus saith unto them, Did ye never read in the scriptures, The stone which the builders rejected, the same is become the head of the corner: this is the Lord's doing, and it is marvellous in our eyes?
43Therefore say I unto you, The kingdom of God shall be taken from you, and given to a nation bringing forth the fruits thereof. 44And whosoever shall fall on this stone shall be broken: but on whomsoever it shall fall, it will grind him to powder.
45And when the chief priests and Pharisees had heard his parables, they perceived that he spake of them. 46But when they sought to lay hands on him, they feared the multitude, because they took him for a prophet.
Matthew 21
Peace