Is it permissible to complete the Qur’an every day? How are we to understand the proven reports which say that the salaf used to complete it in less than three days?
Question

Is it permissible to complete the Qur’an every day? How are we to understand the proven reports which say that the salaf used to complete it in less than three days?
Praise be to Allah.Firstly:
Reading and reciting the Book of Allah, may He be exalted, is one of the greatest acts of worship in Islam. How can that not be the case, when what is read is the words of Allah, may He be exalted? In addition to this honour that is attained by the one who reads the Qur’an, Allah, may He be exalted, has promised the reader great rewards in this world and the hereafter, such as it being guidance and healing for him, that for every letter he will have ten good deeds (hasanaat) to his credit, that the Qur’an will intercede for him on the Day of Resurrection, and other rewards and benefits.
Please see the answer to question no. 141700.
Hence we see that the noble Sahaabah and Taabi‘een, and those of the early generations of this ummah who followed them, were keen to read the Book of their Lord, may He be blessed and exalted, and they would allocate for themselves a portion of it to be read every day.
Despite their eagerness to read the Book of their Lord, they adhered to the guidelines set out by Islamic teachings and did not overstep the bounds, and did not let their eagerness cause them to do anything contrary to prophetic guidance. Hence the majority of scholars are of the view that the Qur’an may be completed every seven days, and whoever has the strength to do more should not complete it in less than three days, except in specific circumstances which we will mention below.
Most of the early generations adhered to the practice of completing it in seven days, following the advice of the Prophet (blessings and peace of Allah be upon him) to ‘Abdullah ibn ‘Amr ibn al-‘Aas.
It was narrated that ‘Abdullah ibn ‘Amr said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Read the Qur’an in a month.” I said: I am able to do better than that… Until he said: “Then read it once every seven days, and do not do any more than that.”
Narrated by al-Bukhaari (4767) and Muslim (1159).
So they did not complete it in less than three days, because the Prophet (blessings and peace of Allah be upon him) discouraged them to do that. 
It was narrated that ‘Abdullah – that is, ibn ‘Amr – said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “No one properly understands who reads the Qur’an in less than three days.”
Narrated by at-Tirmidhi (2949), Abu Dawood (1390) and Ibn Maajah (1347); classed as saheeh by al-Albaani in Saheeh Ibn Maajah.
This is what the Sahaabah understood from the Prophet’s teachings, and the leading scholars followed them in that.
-1-
It was narrated that Ibn Mas‘ood (may Allah be pleased with him) said: Read the Qur’an in seven days and do not read it in less than three days.
Narrated by Sa‘eed ibn Mansoor in his Sunan with a saheeh isnaad, as was stated by al-Haafiz Ibn Hajar in Fadaa’il al-Qur’an (9/78)
-2-
It was narrated from Mu‘aadh ibn Jabal (may Allah be pleased with him) that he regarded it as makrooh to read the Qur’an in less than three days.
Narrated by Abu ‘Ubayd in Fadaa’il al-Qur’an (p. 89)’ classed as saheeh by Ibn Katheer in Fadaa’il al-Qur’an (p. 254).
-3-
Ibn Katheer said:
More than one scholar among the early generations regarded it as makrooh to read the Qur’an in less than three days. This is also the view of Abu ‘Ubayd, Ishaaq ibn Raahawayh and others of the later generations.
Fadaa’il al-Qur’an (p. 254)
In addition to the fact that the one who reads it in less than three days does not understand it properly, he also does not benefit from the sublime and subtle meanings that are understood by the one who reads the Qur’an with reflection, at a measured pace.
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
Reading Qur’an in the manner enjoined instils great faith in the heart, and increases a person in certainty, reassurance and healing.
Majmoo‘ al-Fataawa (7/283).
Secondly:
With regard to what is mentioned in scholarly books about some people completing the Qur’an four times in one day or four times in one night, such reports should be investigated to find out whether they are soundly narrated from their alleged sources, because it is highly unlikely that that happened, as the time is not long enough for that in the first place. The same may be said concerning the claim that some of them completed the Qur’an between Maghrib and ‘Isha’ (!) and other claims that cannot be believed, even if one is able to read quickly. As for reading the entire Qur’an in a single day, that is possible; in fact some of the leading scholars did that – as was narrated from them – in a single rak‘ah.
An-Nawawi (may Allah have mercy on him) said:
As for those who completed the Qur’an in a single rak‘ah, they are innumerable, because they are so many. They include: ‘Uthmaan ibn ‘Affaan, Tameem ad-Daari, and Sa‘eed ibn Jubayr.
Al-Adhkaar (p. 102)
But is the one who does that following the Sunnah of the Prophet (blessings and peace of Allah be upon him), or is he doing something that is not permissible according to Islamic teachings?
The answer is that the one who does that as a habit and way of life is undoubtedly doing something that is contrary to Islamic teachings, and he can only be doing that at the expense of neglecting other shar‘i duties such as prayer, teaching his children, upholding ties of kinship and taking care of his family, or by neglecting working to earn a living.
As for the one who does that occasionally with the aim of reviewing what he has memorised, or to make the most of auspicious times – such as the month of Ramadan – or because he is observing i‘tikaaf (retreat for worship) in the mosque, or because he is focusing on worship for a limited time in Makkah, for example – then that is not contrary to Islamic teaching. It is in this manner that we may interpret the reports narrated from some of the imams (leading scholars), that they completed the Qur’an twice in one day or once in a day; it is not to be understood that this was their way of life at all times.
Ibn Rajab al-Hanbali (may Allah have mercy on him) said:
Qataadah regularly used to complete the Qur’an every seven days, and in Ramadan he would complete it every three days, and in the last ten nights of Ramadan he would complete it every single night. In Ramadan ash-Shaafa‘i used to complete the Qur’an sixty times [i.e., twice a day], reciting it outside of prayer. Something similar was also narrated from Abu Haneefah.
The prohibition on reading the entire Qur’an in less than three days is to be understood as referring to doing that persistently. But at auspicious times, such as the month of Ramadan, and especially on the nights on which Laylat al-Qadr is sought, or in auspicious places, such as Makkah for those who go there and are not residents, then it is mustahabb to read a great deal of Qur’an so as to make the most of that time or that place. This is the view of Ahmad, Ishaaq and other leading scholars, and is indicated by the actions of other scholars, as mentioned above.
Lataa’if al-Ma‘aarif, p. 171
See also the answer to question no. 50781
And Allah knows best.