The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1422
Abu Mas'ud al-Ansari reported: The Messenger of Allah (may peace be upon him) said to us: The one who is well grounded in Allah's Book and is distinguished among them in recitation should act as; Imam for the people. and if they are equally versed in reciting it, then the one who has most knowledge regarding Sunnah; if they are equal regarding the Sunnah, then the earliest one to emigrate; If they emigrated at the same time, then the oldest one in age. No man must lead another in prayer in latter's house or where (the latter) has authority, or sit in his place of honour in his house, except that he gives you permission or with his permission.