The Prophet ? forbade traveling with the Quran to enemy land. So, that it does not fall into their hands, as it will be subject to belittling and underestimation.
On the authority of Abdullah ibn ‘Umar, may Allah be pleased with them both, that the Messenger of Allah ? forbade traveling with the Quran to enemy land. [497] Narrated by Al-Bukhaaree (2990), the wording is his, and Muslim (1869). And in another narration, “For fear that the enemy might attain it.” [498] Narrated by Muslim (1869).
Ibn Abd al-Barr says, “It is known that the purity of the Quran and its glorification is to keep it away from dirt and impurities, and to be with the disbelievers, is exposing it to that and insulting it. All of them are unclean, they do not wash from impurity, nor do they detest a dead carrion.” [499] At-Tamheed, (15/255). And belittling the Quran may be by words, or it may be by actions.
The verbal disrespect for the Quran is to insult it, disbelieve one of its news, or ridicule one of its ayaat. The practical disrespect for the Quran is for a person to deliberately do something that includes contempt or disdain for this Quran or a drop in its sanctity, such as placing the Quran under his feet, or throwing it in the dirt, or trying to change it and replace it with an increase or decrease of its contents.

From the reports of the imams of Mathhabs on this:
Muhammad ibn Ismail ar-Rasheed al-Hanafee says, “Whoever makes light of the Quran, the mosque, or similar things that are glorified in the divine law, then he has disbelieved; and whoever puts his foot on the Mus-haf when swearing an oath and disrespectfully, he has committed Kufr.” [500] “Alfaadh al-Kufr” (p.: 29) (included in the book “Al-Jaami’ fi Alfaazh al-Kufr”), and Mulla ‘Alee Qaaree said, commenting on the last sentence: It is not hidden that his saying: by swearing is a real restriction; It can be comprehended. Sharh al-Fiqh al-Akbar, (p.: 278).
Ad-Dardeer al-Maalikee mentioned one of the causes of apostasy, “Reciting a copy of the Quran or some of it, even if it is a word, and likewise burning it in disregard, not for protection... And like throwing it is leaving it in a filthy place, even if it is pure as spit, or smearing it with it,... And like the Mus-haf is hadeeth, the names of Allah Almighty, hadeeth books, and also books of jurisprudence if it is in order to disrespect the Sharee’a.” [501] Hashiyah Al-Saawee ‘ala Al-Sharh Al-Sagheer, (4/433).
An-Nawawee Ash-Shaafi’ee says, “Acts that necessitate infidelity are those that are intentional and an explicit mockery of religion, such as… throwing the Quran into the dirt.” [502] Rawdat Al-Taalibeen, (10/64).
Al-Bahootee al-Hanbalee considered the following as nullifiers of Islam, “Or an insult to the Quran was found from him, or a request to contradict it, or a claim that it is different, or capable of something like it, or the overthrow of its sanctity; in this respect, he has disbelieved.” [503] Kashshaaf al-Qinaa’, (14/228).
Ibn Baaz said: “Similarly, he who insults the Quran, taints it with impurity, or sits on it knowing that it is the Book of Allah.  This is evidence that this man has no faith, even if he claims to have faith. If he had a true belief, it would have prevented him from doing this act that necessitates his infidelity.” [504] Majmoo’ Fataawaa Ibn Baaz, (3/38).
Belittling the Quran is one of the nullifiers of faith, for several reasons: Of which:
1-   Faith is based on glorifying Allah Almighty and venerating His words, while disrespect is belittling and mocking which contradicts that.
Allah Almighty said, “Say, ‘Is it Allah and His signs and His Messenger that you were mocking?’”  At-Tawbah : 65-66
Ibn Qudaamah transmitted the agreement of Muslims to venerate and revere the Quran. [505] Hikayat al-Munazharah fi al-Qur’an ma’ Ahl al-Bida’ah, (p.: 49).
Ibn Taymiyyah said, “Submitting is reverence and honour, and belittling is insult and humiliation, and these are two opposites.  Whenever one of them is in the heart, the other is absent. Thus, it became known that belittling and degrading contradicts faith as the opposite contradicts the opposite.” [506] Al-Saarim Al-Maslool, (3/969).
2-   Belittling the Quran is a denial of Allah Almighty in His news and contradicts what Allah Almighty has commanded such as glorifying His words, the Mighty and Majestic, and belittling the Quran is disregarding those whom the Most High spoke to. [507] Mughnee Al-Muhtaaj, by Al-Sharbeenee (5/431).
Allah Almighty states, “Indeed, it is We who sent down the message i.e., the Qur’?n, and indeed, We will be its guardian.” Al-Hijr: 9
Aboo As-Sa’ood says, “‘And We will be its guardian,’ meaning from everything that is not worthy of it, so their denial of it and their mockery of it enter into it initially. Thus, it is a warning for the mockers. As for mere preservation from misrepresentation, addition and deficiency, and the like, it is not in accordance with the situation. The best is to take the meaning of preservation from all what it can be dispraised about such as slandering and arguing about its truth. It may be meant that its protection signifies miraculous inimitability as a proof of revelation from Allah Almighty; for if it were from other than Allah, it would have been increased, decreased, and differed.” [508] Tafseer of Abee Al-Sa’ood, (5/68). See: “Fath al-Qadeer” by al-Shawkaanee (3/147).
3-   Underestimating the Quran – through perversion or substitution - is belittling the religion, a demolition of the foundations and branches of this Sharee’a, and it is an attack on the integrity and perfection of the religion of Islam.
Ibn Hazm says, “The religion has been completed, it cannot be added to it, nor can it be decreased and neither changed. The Almighty said, “Today I have perfected your religion for you,” and the Most High said, “There is no changing for the Words of Allah,” and decrease and addition are an act of changing.” [509] Al-Muhalla, (1/26).
Muhammad ibn Abdul Wahab says, “Whoever believes in the invalidity of its preservation the Quran from dropping out, and believes what is not part of it as its part; then he has disbelieved. This necessitates the upliftment of the trust in the whole Quran, which leads to the demolition of religion, and necessitates for them not to use it for proof, and not to worship by reciting it, for the possibility of change. How insidious are the words of a people which destroy their religion!” [510] Risaalah fi ar-Radd ‘ala ar-Raafidah, (Printed among the books of Shaykh Muhammad bin ‘Ad al-Wahhaab, Part Twelve) (p.: 15).
4-   The scholars are unanimously agreed on the infidelity of the one who underestimates the Quran and on his departure from the religion
‘Iyaad says, “Know that whoever belittles the Quran or the Mus-haf or anything of it, or insults them, or denies it, or a letter or a ayah from it, or disaffirms it or something of it, or denies something of what it has declared or of a ruling, or news; or he establishes what it has negated or he negates what it has established, knowing that he is aware of that; or doubts anything of that - then he is an unbeliever according to the people of knowledge by consensus; Allah Almighty said, “Indeed it is a mighty Book. Falsehood cannot approach it from before it or from behind it; it is a revelation from a Lord who is Wise and Praiseworthy.” Fussilat: 42.” [511] Ash-Shifaa, (2/304)
Ibn Taymiyyah said, “The Muslims have agreed that whoever makes light of the Mus-haf, such as throwing it into the stuffing, or kicking it with his foot in disgrace, is an infidel whose blood is permissible.” [512] Majmoo’ Al-Fataawaa, (8/425).