Sahih Bukhari
Virtues of the Quran
Volume: 006 / Book Number: 061 / Hadith Number: 525
arrated 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."