Musnad Ahmad 32:1998

Yahya ibn Sa'id narrated to us, from Shu'bah, Qatadah narrated to us, and Hajjaj narrated to us, he said: I heard Shu'bah narrating from Qatadah, from Anas, who said: "The Quran was collected during the time of the Messenger of Allah, may Allah bless him and grant him peace, by four—Yahya said: All of them from the Ansar—: Ubayy ibn Ka'b, Mu'adh ibn Jabal, Zayd ibn Thabit, and Abu Zayd." He said: I said: "Who is Abu Zayd?" He said: "One of my paternal uncles."