Volume 7 · Book 61 · Hadith 525
Narrated Qatada: I asked Anas bin Malik: "Who collected the Qur'an at the time of the Prophet ?" He replied, "Four, all of whom were from the Ansar: Ubai bin Ka'b, Mu'adh bin Jabal, Zaid bin Thabit and Abu Zaid."
— Sahih Bukhari, Volume 7, Book 61: Virtues of the Qur'an, Hadith #525