Musnad Ahmad 31:794

Yazid narrated to us, Hammam ibn Yahya narrated to us, and my father and Abu Badr said, from Sa’id, from Qatadah, from Abu Nadrah, from Abu Sa’id al-Khudri, from the Prophet, peace and blessings of Allah be upon him, who said: "If three are gathered, 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."