Proof that some Companions memorized Quran during lifetime of Prophet Muhammad
5-3-2016 | IslamWeb
Question:
What Is the Proof That Some of the Companions Memorized the Entire Quran before the Death of the Prophet, sallallaahu ʻalayhi wa sallam?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.
Many of the Companions memorized the Quran during the lifetime of the Prophet, sallallaahu ʻalayhi wa sallam, including the four rightly-guided Caliphs (Abu Bakr, ʻUmar, ʻUthmaan, and ʻAli), ʻAbd Ar-Rahmaan ibn ʻAwf, Az-Zubayr ibn Al-ʻAwwaam, Muʻaath ibn Jabal, Ubayy ibn Kaʻb, Zayd ibn Thaabit, Abu Zayd, ʻAbdullaah ibn ʻAmr, and others 
. Proof of their large number is that those who were killed of them in the Yamaamah battle were seventy, as mentioned by Al-Qurtubi 
and other scholars. It has also been narrated that a large number of the Companions who memorized the Quran were killed at Bi'r Maʻoonah during the lifetime of the Prophet, sallallaahu ʻalayhi wa sallam.
It was narrated that Zayd ibn Thaabit 
who was one of those who used to write the Divine Revelation, said:
“Abu Bakr sent for me after the (heavy) casualties among the warriors (of the battle) of Yamaamah. ʻUmar was present with Abu Bakr who said, 'ʻUmar has come to me and said that the people have suffered heavy casualties on the day of Yamaamah, and I am afraid that there will be more casualties among the qurraa' (those who know and memorize the Quran by heart) at other battlefields, whereby a large part of the Quran may be lost, unless you collect it. And I am of the opinion that you should collect the Quran.' Abu Bakr added, 'I said to ʻUmar, 'How can I do something which the Messenger of Allaah, sallallaahu ʻalayhi wa sallam, has not done?' ʻUmar said, 'By Allaah, it is indeed a good thing.' So ʻUmar kept on pressing, trying to persuade me to accept his proposal till Allaah opened my bosom for it and I had the same opinion as ʻUmar.'' Abu Bakr then said to me, 'You are a wise young man and we do not suspect you (of telling lies or err out of forgetfulness), and you used to write the Divine Inspiration for the Messenger of Allaah, sallallaahu ʻalayhi wa sallam. Therefore, look for the Quran and collect it (in one manuscript).' By Allaah, if he (Abu Bakr) had ordered me to shift one of the mountains (from its place), it would not have been harder for me than what he had ordered me concerning the collection of the Quran. I said to both of them, 'How dare you do a thing which the Prophet 
has not done?' Abu Bakr said, 'By Allaah, it is indeed a good thing. So I kept on arguing with him about it till Allaah opened my bosom for that which He had opened the bosoms of Abu Bakr and ʻUmar for. So I started locating Quran material and collecting it from parchments, scapula, leaf-stalks of date palms, and the memories of men (who knew it by heart). I found with Abu Khuzaymah Al-Ansaari two verses of Soorah At-Tawbah which I had not found with anybody else: {There has certainly come to you a Messenger from among yourselves...} (Quran 9:128) until the end of the chapter. The manuscript on which the Quran was collected remained with Abu Bakr till Allaah took him unto Him, and then with ʻUmar till Allaah took him unto Him, and finally it remained with Hafsah, ʻUmar's daughter.” [Al-Bukhari]
Among those who memorized the Quran were the members of the committee that ʻUthmaan assembled to write the standardized copy of the Quran (the mus-haf). Al-Haafith Ibn Hajar narrated the following (with a good chain of narration) on the authority of Muhammad ibn Seereen and Katheer ibn Aflah 
“When ʻUthmaan wanted to collect the Quran in one standardized copy, he assembled a committee of twelve men from the Quraysh and the Ansaar, including Ubayy ibn Kaʻb and Zayd ibn Thaabit, under the supervision of ʻUthmaan. Whenever they disagreed on a given verse, they would delay discussing it.” [Fat-h Al-Baari]
Manaahil Al-ʻIrfaan reads:
“There was a great number of the Companions who memorized the Quran during the lifetime of the Messenger, including the four Rightly-guided Caliphs, Talhah, Saʻd, Ibn Masʻood, Huthayfah, Saalim (the freed slave of Abu Huthayfah), Abu Hurayrah, Ibn ʻUmar, Ibn ʻAbbaas, ʻAmr ibn Al-ʻAas and his son ʻAbdullaah, Muʻaawiyyah, Ibn Az-Zubayr, ʻAbdullaah ibn As-Saa'ib, ʻAa'ishah, Hafsah, and Umm Salamah, and they were all from the Muhaajireen (emigrants) all. Those who memorized the Quran in his lifetime from the Ansaar were Ubayy ibn Kaʻb, Muʻaath ibn Jabal, Zayd ibn Thaabit, Abu Ad-Dardaa', Majmaʻ ibn Haarithah, Anas ibn Maalik, and Abu Zayd, about whom Anas was asked and said, 'He is one of my cousins all...' It was also said that some of them completed the memorization of the Quran after the death of the Prophet, sallallaahu ʻalayhi wa sallam.”
Allaah knows best.