Asim narrates from Sayyiduna Amr bin Salamah (may Allah be pleased with him) that when my people returned from the Prophet (peace and blessings be upon him), he (peace and blessings be upon him) had said: "Let the one among you who has read the most Qur'an lead you in prayer." He says: They called me and taught me bowing and prostration. I would lead them in prayer while I was a boy, and I had a torn sheet on me, so they would say to my father: "Will you not cover your son's backside from us?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5138
Sayyiduna Amr bin Salamah (may Allah be pleased with him) says that my people came to the Prophet (peace and blessings be upon him). When they had read the Qur'an and fulfilled their needs, they asked who should lead them in prayer. He (peace and blessings be upon him) said: "The one who has memorised the most Qur'an." When they came back to their people, they asked about this, but no one had memorised more Qur'an than me. They put me forward while I was a boy, and I would lead them in prayer. Whenever there was a gathering, I was their imam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5139
Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) and Sayyiduna Abu Hurayrah (may Allah be pleased with him) both say that the Messenger of Allah (peace and blessings be upon him) said: "I have been commanded to fight the people until they say 'La ilaha illallah' (There is no god worthy of worship except Allah). When they say this word, they have protected their wealth and their blood from me, except by its right, and their reckoning is with Allah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5140