Musnad Ahmad 28:314

Waki' narrated to us, he said: Al-A'mash narrated to us, from Abu Wa'il, from Masruq, from Abdullah ibn Amr, he said: The Messenger of Allah, may Allah bless him and grant him peace, said: "Take the Quran from four: from Ibn Umm 'Abd—and he began with him—and from Mu'adh ibn Jabal, and Ubayy ibn Ka'b, and Salim, the freed slave of Abu Hudhayfah."