Musnad Ahmad 32:1343

Rawh narrated to us, Sa'id ibn Abi 'Aruba narrated to us, from Qatada, who said: Anas ibn Malik narrated to us, that the Prophet of Allah, peace and blessings of Allah be upon him, said to Ubayy ibn Ka'b: "Indeed, Allah has commanded me to recite the Quran to you, or to read the Quran upon you." He said: "Has Allah named me to you?" He said: "Yes." He said: "Have I been mentioned in the presence of the Lord of the worlds?" He said: "Yes." He said: "Then his eyes overflowed with tears."