A Muslim is obliged to memorize from the Qur’an the portion needed to recite in Prayer so that his Prayer is valid. Memorizing the Qur’an is a collective duty. In his book entitled Al-Majmu`, Imam An-Nawawi states, “Memorizing from the Qur’an more than Al-Fatihah is more meritorious than performing voluntary Prayer, as its memorization is a collective duty.” Furthermore, worshiping Allah through reading the Qur’an from a mushaf is better than reciting from memory. In addition, the Qur’an will intercede for its reader on the Day of Resurrection when the Qur’an becomes his constitution and course of life, that is, when he becomes a follower of its high moral standards and an abider by its codes of behavior.
Dr. Ahmad Taha Rayyan, professor of comparative jurisprudence at Al-Azhar University, states: “The performer of Prayer must memorize from the Qur’an what is sufficient to make his Prayer valid, and if he cannot, he will not be deemed sinning. In this regard, Ibn Abu Awfa (may Allah be pleased with him) narrated: A man came to Allah’s Messenger (peace and blessings be upon him) and said, “I can memorize nothing from the Qur’an, so teach me what may suffice me.” The Prophet (peace and blessings be upon him) replied, “Say, ‘Subhana Allah, wal-hamdu lillah, wa la ilaha illa Allah, wa Allahu akbar, wa la hawla wa la quwwata illa billah (Glorified be Allah, praise is due to Allah, there is no god but Allah, Allah is the Greatest, there is no power or strength save in Allah)’” (Reported by An-Nasa’i).
As for memorizing the Qur’an as an act of worship, it is recommendable but not obligatory. This is because only a few of the Messenger’s Companions memorized the whole of the Qur’an. Moreover, worshiping Allah through the Qur’an can be fulfilled by memorizing some of its surahs and it can be also achieved by reading the Qur’an from the mushaf. What is more, some scholars state that reading the Qur’an from the mushaf is more rewardable than reciting from memory, for looking into the mushaf is an act of worship one should do. Commenting on this opinion, Imam An-Nawawi said, “This is the opinion adopted by the Shafi`i scholars and the Salaf (early Muslim scholars), and I have not found any disagreement concerning this opinion.” About the virtue of reading the Qur’an from the mushaf, An-Nawawi further depended on the hadith narrated on the authority of Aws Ath-Thaqafi that the Prophet (peace and blessings be upon him) said, “One’s reading from one’s memory confers thousand degrees and one’s reading from the mushaf confers more than two thousand degrees” (Reported by At-Tabarani and Al-Bayhaqi). Moreover, Abu `Ubayd reported through a reliable chain of transmission that the Prophet (peace and blessings be upon him) said, “The merit of reading the Qur’an from the mushaf when compared to reading it from memory is like the merit of an obligation compared to a supererogatory act of worship.”
So, after knowing the excellence of reading the Qur’an from the mushaf but you want to gain the reward for reading it from memory, you should memorize some of the short surahs or some verses from the long ones. Abu Hurayrah (may Allah be pleased with him) is reported to have said that Allah’s Messenger (peace and blessings be upon him) said, “Would anyone of you like, when he returns to his family, to find there three large, fat, pregnant she-camels?” We said, “Yes.” Upon this, he said, “Three verses that one of you recites in his Prayer are better for him than three large, fat, pregnant she-camels” (Reported by Muslim).
Furthermore, the legal texts tackling the intercession of the Qur’an do not stipulate that it be kept by heart. This is demonstrated in the hadith reported by Imam Abu `Ubayd with his chain of transmission on the authority of Anas. In this hadith, Anas (may Allah be pleased with him) narrated that the Prophet (peace and blessings be upon him) said, “The Qur’an is an intercessor whose intercession will be accepted, and (it is) a claimant whose claim will be believed. Whoever places it before him (that is, abides by its teachings), will be guided by it to Paradise; and whoever places it behind him (that is, deserts what it enjoins), will be driven by it to the Hellfire.”