Anas told that in the time of God's messenger four people knew the whole Quran:
Ubayy b. Ka'b, Mu'adh b. Jabal, Zaid b. Thabit and Abu Zaid. Anas was asked who Abu Zaid was and replied that he was one of his paternal uncles. Bukhari and Muslim.
Hadith Referenceمشكوة المصابيح / كتاب المناقب / 6204
Hadith Gradingالألبانی:مُتَّفق عَلَيْهِ | زبیر علی زئی:متفق عليه
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «متفق عليه، رواه البخاري (3810) و مسلم (119/ 2460)»