Musnad Abu Ya'la al-Mawsili 42:318

Zuhayr narrated to us, Abu Badr narrated to us, from Sa'id ibn Abi 'Arubah, from Qatadah, from Abu Nadrah, from Abu Sa'id al-Khudri, that the Messenger of Allah (may Allah bless him and grant him peace) said: "If there are three, 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."