Musnad Abu Ya'la al-Mawsili 42:346

Zuhayr narrated to us, Affan narrated to us, Hammam narrated to us, Qatadah narrated to us, from Abu Nadrah, from Abu Sa’id al-Khudri, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If three are gathered, then let one of them lead them in prayer, and the most entitled of them to the leadership is the one who is most proficient in reciting the Quran."