Mishkat al-Masabih 30 Fine Qualities كتاب المناقب 218

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.