وَعَن أنس قَالَ: جَمَعَ الْقُرْآنَ عَلَى عَهْدِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَرْبَعَةٌ: أُبَيُّ بْنِ كَعْبٍ وَمُعَاذِ بْنِ جَبَلٍ وَزَيْدِ بْنِ ثَابِتٍ وَأَبُو زَيْدٍ قِيلَ لِأَنَسٍ: مَنْ أَبُو زَيْدٍ؟ قَالَ: أحد عمومتي. مُتَّفق عَلَيْهِ

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[*]. *Ibn `Abd al-Barr, Isti'ab, p. 650, says he was Qais b. as-Sakan. Bukhari and Muslim.