Carefulness of the prophet in collection and compilation of Quran

At first, Quran was preserved by heart and it started from the prophet (peace of Allah be upon him and his descendants). All attempt of the prophet was to learn Quran, to preserve it and then he read it for people patiently so that they could learn, act and preserve it.
The prophet (peace of Allah be upon him and his descendants) tried a lot to learn and memorize as Quran states
لَا تُحَرِّكْ بِهِ لِسَانَكَ لِتَعْجَلَ بِهِ
Move not thy tongue concerning the (Qur´an) to make haste therewith.
إِنَّ عَلَيْنَا جَمْعَهُ وَقُرْآنَهُ
.It is for Us to collect it and to promulgate it
Before Quran descending finished, the prophet read it for people;
فَتَعَالَى اللَّهُ الْمَلِكُ الْحَقُّ ۗ وَلَا تَعْجَلْ بِالْقُرْآنِ مِن قَبْلِ أَن يُقْضَىٰ إِلَيْكَ وَحْيُهُ ۖ وَقُل رَّبِّ زِدْنِي عِلْمًا
High above all is Allah, the King, the Truth! Be not in haste with the Qur´an before its revelation to thee is completed, but say, "O my Lord! advance me in knowledge.
The verses of Quran show that the prophet tried a lot in reciting Quran and considered thinking about the content of the verses of Quran necessary;
أَلَيْسَ اللَّهُ بِأَحْكَمِ الْحَاكِمِينَ
؟Is not Allah the wisest of judges
أَوَلَمْ يَنظُرُوا فِي مَلَكُوتِ السَّمَاوَاتِ وَالْأَرْضِ وَمَا خَلَقَ اللَّهُ مِن شَيْءٍ وَأَنْ عَسَىٰ أَن يَكُونَ قَدِ اقْتَرَبَ أَجَلُهُمْ ۖ فَبِأَيِّ حَدِيثٍ بَعْدَهُ يُؤْمِنُونَ
Do they see nothing in the government of the heavens and the earth and all that Allah hath created? (Do they not see) that it may well be that their terms is nigh drawing to an end? In what message after this will they then believe.
فَأَلْهَمَهَا فُجُورَهَا وَتَقْوَاهَا
.And its enlightenment as to its wrong and its right
الَّذِينَ آتَيْنَاهُمُ الْكِتَابَ يَتْلُونَهُ حَقَّ تِلَاوَتِهِ أُولَٰئِكَ يُؤْمِنُونَ بِهِ ۗ وَمَن يَكْفُرْ بِهِ فَأُولَٰئِكَ هُمُ الْخَاسِرُونَ
Those to whom We have sent the Book study it as it should be studied: They are the ones that believe therein: Those who reject faith therein,- the loss is their own.
The prophet read Quran not only in praying also in all times, during travel and in time of fighting and encouraged people to read it. The verses of Quran attracted Arabic people and it had strong effect. Therefore, unbelievers tried that none listened to the verses of Quran;
وَقَالَ الَّذِينَ كَفَرُوا لَا تَسْمَعُوا لِهَٰذَا الْقُرْآنِ وَالْغَوْا فِيهِ لَعَلَّكُمْ تَغْلِبُونَ
The Unbelievers say: "Listen not to this Qur´an, but talk at random in the midst of its (reading), that ye may gain the upper hand.
Quran training was comprehensive in early days. Abu Musa Ashari says '' the messenger of God went to circles of Quran training in night time and he listened to their Quran reciting. He also taught his family to learn and listen to it''.
Moreover, the prophet sent his companions to far places so that they could teach Quran to them.
Persons that had learned Quran had prominent rank according to the prophet of God. He expressed all points in preaching Quran and in encouraging the companions to memorize and act Quran. Quran states
وَمَا كَانَ الْمُؤْمِنُونَ لِيَنفِرُوا كَافَّةً ۚ فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍ مِّنْهُمْ طَائِفَةٌ لِّيَتَفَقَّهُوا فِي الدِّينِ وَلِيُنذِرُوا قَوْمَهُمْ إِذَا رَجَعُوا إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ
Nor should the Believers all go forth together: if a contingent from every expedition remained behind, they could devote themselves to studies in religion, and admonish the people when they return to them,- that thus they (may learn) to guard themselves (against evil).
أَذَانٌ مِّنَ اللَّهِ وَرَسُولِهِ إِلَى النَّاسِ يَوْمَ الْحَجِّ الْأَكْبَرِ أَنَّ اللَّهَ بَرِيءٌ مِّنَ الْمُشْرِكِينَ ۙ وَرَسُولُهُ ۚ فَإِن تُبْتُمْ فَهُوَ خَيْرٌ لَّكُمْ ۖ وَإِن تَوَلَّيْتُمْ فَاعْلَمُوا أَنَّكُمْ غَيْرُ مُعْجِزِي اللَّهِ ۗ وَبَشِّرِ الَّذِينَ كَفَرُوا بِعَذَابٍ أَلِيمٍ
And an announcement from Allah and His Messenger, to the people (assembled) on the day of the Great Pilgrimage,- that Allah and His Messenger dissolve (treaty) obligations with the Pagans. If then, ye repent, it were best for you; but if ye turn away, know ye that ye cannot frustrate Allah. And proclaim a grievous penalty to those who reject Faith.
فَإِذَا انسَلَخَ الْأَشْهُرُ الْحُرُمُ فَاقْتُلُوا الْمُشْرِكِينَ حَيْثُ وَجَدتُّمُوهُمْ وَخُذُوهُمْ وَاحْصُرُوهُمْ وَاقْعُدُوا لَهُمْ كُلَّ مَرْصَدٍ ۚ فَإِن تَابُوا وَأَقَامُوا الصَّلَاةَ وَآتَوُا الزَّكَاةَ فَخَلُّوا سَبِيلَهُمْ ۚ إِنَّ اللَّهَ غَفُورٌ رَّحِيمٌ
But when the forbidden months are past, then fight and slay the Pagans wherever ye find them, an seize them, beleaguer them, and lie in wait for them in every stratagem (of war); but if they repent, and establish regular prayers and practise regular charity, then open the way for them: for Allah is Oft-forgiving, Most Merciful.
قُلْ إِن كَانَ آبَاؤُكُمْ وَأَبْنَاؤُكُمْ وَإِخْوَانُكُمْ وَأَزْوَاجُكُمْ وَعَشِيرَتُكُمْ وَأَمْوَالٌ اقْتَرَفْتُمُوهَا وَتِجَارَةٌ تَخْشَوْنَ كَسَادَهَا وَمَسَاكِنُ تَرْضَوْنَهَا أَحَبَّ إِلَيْكُم مِّنَ اللَّهِ وَرَسُولِهِ وَجِهَادٍ فِي سَبِيلِهِ فَتَرَبَّصُوا حَتَّىٰ يَأْتِيَ اللَّهُ بِأَمْرِهِ ۗ وَاللَّهُ لَا يَهْدِي الْقَوْمَ الْفَاسِقِينَ
Say: If it be that your fathers, your sons, your brothers, your mates, or your kindred; the wealth that ye have gained; the commerce in which ye fear a decline: or the dwellings in which ye delight - are dearer to you than Allah, or His Messenger, or the striving in His cause;- then wait until Allah brings about His decision: and Allah guides not the rebellious.
يَا أَيُّهَا الَّذِينَ آمَنُوا إِنَّ كَثِيرًا مِّنَ الْأَحْبَارِ وَالرُّهْبَانِ لَيَأْكُلُونَ أَمْوَالَ النَّاسِ بِالْبَاطِلِ وَيَصُدُّونَ عَن سَبِيلِ اللَّهِ ۗ وَالَّذِينَ يَكْنِزُونَ الذَّهَبَ وَالْفِضَّةَ وَلَا يُنفِقُونَهَا فِي سَبِيلِ اللَّهِ فَبَشِّرْهُم بِعَذَابٍ أَلِيمٍ
O ye who believe! there are indeed many among the priests and anchorites, who in Falsehood devour the substance of men and hinder (them) from the way of Allah. And there are those who bury gold and silver and spend it not in the way of Allah: announce unto them a most grievous penalty.
إِنَّ عِدَّةَ الشُّهُورِ عِندَ اللَّهِ اثْنَا عَشَرَ شَهْرًا فِي كِتَابِ اللَّهِ يَوْمَ خَلَقَ السَّمَاوَاتِ وَالْأَرْضَ مِنْهَا أَرْبَعَةٌ حُرُمٌ ۚ ذَٰلِكَ الدِّينُ الْقَيِّمُ ۚ فَلَا تَظْلِمُوا فِيهِنَّ أَنفُسَكُمْ ۚ وَقَاتِلُوا الْمُشْرِكِينَ كَافَّةً كَمَا يُقَاتِلُونَكُمْ كَافَّةً ۚ وَاعْلَمُوا أَنَّ اللَّهَ مَعَ الْمُتَّقِينَ
The number of months in the sight of Allah is twelve (in a year)- so ordained by Him the day He created the heavens and the earth; of them four are sacred: that is the straight usage. So wrong not yourselves therein, and fight the Pagans all together as they fight you all together. But know that Allah is with those who restrain themselves.
إِنَّمَا النَّسِيءُ زِيَادَةٌ فِي الْكُفْرِ ۖ يُضَلُّ بِهِ الَّذِينَ كَفَرُوا يُحِلُّونَهُ عَامًا وَيُحَرِّمُونَهُ عَامًا لِّيُوَاطِئُوا عِدَّةَ مَا حَرَّمَ اللَّهُ فَيُحِلُّوا مَا حَرَّمَ اللَّهُ ۚ زُيِّنَ لَهُمْ سُوءُ أَعْمَالِهِمْ ۗ وَاللَّهُ لَا يَهْدِي الْقَوْمَ الْكَافِرِينَ
Verily the transposing (of a prohibited month) is an addition to Unbelief: the Unbelievers are led to wrong thereby: for they make it lawful one year, and forbidden another year, in order to adjust the number of months forbidden by Allah and make such forbidden ones lawful. The evil of their course seems pleasing to them. But Allah guideth not those who reject Faith.
إِلَّا تَنصُرُوهُ فَقَدْ نَصَرَهُ اللَّهُ إِذْ أَخْرَجَهُ الَّذِينَ كَفَرُوا ثَانِيَ اثْنَيْنِ إِذْ هُمَا فِي الْغَارِ إِذْ يَقُولُ لِصَاحِبِهِ لَا تَحْزَنْ إِنَّ اللَّهَ مَعَنَا ۖ فَأَنزَلَ اللَّهُ سَكِينَتَهُ عَلَيْهِ وَأَيَّدَهُ بِجُنُودٍ لَّمْ تَرَوْهَا وَجَعَلَ كَلِمَةَ الَّذِينَ كَفَرُوا السُّفْلَىٰ ۗ وَكَلِمَةُ اللَّهِ هِيَ الْعُلْيَا ۗ وَاللَّهُ عَزِيزٌ حَكِيمٌ
If ye help not (your leader), (it is no matter): for Allah did indeed help him, when the Unbelievers drove him out: he had no more than one companion; they two were in the cave, and he said to his companion, "Have no fear, for Allah is with us": then Allah sent down His peace upon him, and strengthened him with forces which ye saw not, and humbled to the depths the word of the Unbelievers. But the word of Allah is exalted to the heights: for Allah is Exalted in might, Wise.
لَوْ كَانَ عَرَضًا قَرِيبًا وَسَفَرًا قَاصِدًا لَّاتَّبَعُوكَ وَلَٰكِن بَعُدَتْ عَلَيْهِمُ الشُّقَّةُ ۚ وَسَيَحْلِفُونَ بِاللَّهِ لَوِ اسْتَطَعْنَا لَخَرَجْنَا مَعَكُمْ يُهْلِكُونَ أَنفُسَهُمْ وَاللَّهُ يَعْلَمُ إِنَّهُمْ لَكَاذِبُونَ
If there had been immediate gain (in sight), and the journey easy, they would (all) without doubt have followed thee, but the distance was long, (and weighed) on them. They would indeed swear by Allah, "If we only could, we should certainly have come out with you": They would destroy their own souls; for Allah doth know that they are certainly lying.
إِنَّمَا الصَّدَقَاتُ لِلْفُقَرَاءِ وَالْمَسَاكِينِ وَالْعَامِلِينَ عَلَيْهَا وَالْمُؤَلَّفَةِ قُلُوبُهُمْ وَفِي الرِّقَابِ وَالْغَارِمِينَ وَفِي سَبِيلِ اللَّهِ وَابْنِ السَّبِيلِ ۖ فَرِيضَةً مِّنَ اللَّهِ ۗ وَاللَّهُ عَلِيمٌ حَكِيمٌ
Alms are for the poor and the needy, and those employed to administer the (funds); for those whose hearts have been (recently) reconciled (to Truth); for those in bondage and in debt; in the cause of Allah; and for the wayfarer: (thus is it) ordained by Allah, and Allah is full of knowledge and wisdom.
كَالَّذِينَ مِن قَبْلِكُمْ كَانُوا أَشَدَّ مِنكُمْ قُوَّةً وَأَكْثَرَ أَمْوَالًا وَأَوْلَادًا فَاسْتَمْتَعُوا بِخَلَاقِهِمْ فَاسْتَمْتَعْتُم بِخَلَاقِكُمْ كَمَا اسْتَمْتَعَ الَّذِينَ مِن قَبْلِكُم بِخَلَاقِهِمْ وَخُضْتُمْ كَالَّذِي خَاضُوا ۚ أُولَٰئِكَ حَبِطَتْ أَعْمَالُهُمْ فِي الدُّنْيَا وَالْآخِرَةِ ۖ وَأُولَٰئِكَ هُمُ الْخَاسِرُونَ
As in the case of those before you: they were mightier than you in power, and more flourishing in wealth and children. They had their enjoyment of their portion: and ye have of yours, as did those before you; and ye indulge in idle talk as they did. They!- their work are fruitless in this world and in the Hereafter, and they will lose (all spiritual good).
يَحْلِفُونَ بِاللَّهِ مَا قَالُوا وَلَقَدْ قَالُوا كَلِمَةَ الْكُفْرِ وَكَفَرُوا بَعْدَ إِسْلَامِهِمْ وَهَمُّوا بِمَا لَمْ يَنَالُوا ۚ وَمَا نَقَمُوا إِلَّا أَنْ أَغْنَاهُمُ اللَّهُ وَرَسُولُهُ مِن فَضْلِهِ ۚ فَإِن يَتُوبُوا يَكُ خَيْرًا لَّهُمْ ۖ وَإِن يَتَوَلَّوْا يُعَذِّبْهُمُ اللَّهُ عَذَابًا أَلِيمًا فِي الدُّنْيَا وَالْآخِرَةِ ۚ وَمَا لَهُمْ فِي الْأَرْضِ مِن وَلِيٍّ وَلَا نَصِيرٍ
They swear by Allah that they said nothing (evil), but indeed they uttered blasphemy, and they did it after accepting Islam; and they meditated a plot which they were unable to carry out: this revenge of theirs was (their) only return for the bounty with which Allah and His Messenger had enriched them! If they repent, it will be best for them; but if they turn back (to their evil ways), Allah will punish.
them with a grievous penalty in this life and in the Hereafter: They shall have none on earth to protect or help them.
يَعْتَذِرُونَ إِلَيْكُمْ إِذَا رَجَعْتُمْ إِلَيْهِمْ ۚ قُل لَّا تَعْتَذِرُوا لَن نُّؤْمِنَ لَكُمْ قَدْ نَبَّأَنَا اللَّهُ مِنْ أَخْبَارِكُمْ ۚ وَسَيَرَى اللَّهُ عَمَلَكُمْ وَرَسُولُهُ ثُمَّ تُرَدُّونَ إِلَىٰ عَالِمِ الْغَيْبِ وَالشَّهَادَةِ فَيُنَبِّئُكُم بِمَا كُنتُمْ تَعْمَلُونَ
They will present their excuses to you when ye return to them. Say thou: "Present no excuses: we shall not believe you: Allah hath already informed us of the true state of matters concerning you: It is your actions that Allah and His Messenger will observe: in the end will ye be brought back to Him Who knoweth what is hidden and what is open: then will He show you the truth of all that ye did.
The prophet trained Quran the companions and persons that had just become Muslim as much as he could. He tried to recite Quran properly and had special attention in order to elucidate matters and problems as Quran states
بِالْبَيِّنَاتِ وَالزُّبُرِ ۗ وَأَنزَلْنَا إِلَيْكَ الذِّكْرَ لِتُبَيِّنَ لِلنَّاسِ مَا نُزِّلَ إِلَيْهِمْ وَلَعَلَّهُمْ يَتَفَكَّرُونَ
(We sent them) with Clear Signs and Books of dark prophecies; and We have sent down unto thee (also) the Message; that thou mayest explain clearly to men what is sent for them, and that they may give thought.
فَاذْكُرُونِي أَذْكُرْكُمْ وَاشْكُرُوا لِي وَلَا تَكْفُرُونِ
Then do ye remember Me; I will remember you. Be grateful to Me, and reject not Faith.
Naturally, the verses of Quran needed explanation and elucidation so that they could be understood. All of the principles of the religion are expressed in Quran and the prophet tried to explain these principles. All attempt and carefulness of the prophet had a lot of positive effects in training and purifying human.