Sunnah.com reference : Book 2, Hadith 317English translation : Book 2, Hadith 407Arabic reference : Book 2, Hadith 412
Narrated 'Amr bin Salimah (RA):
My father said, "I have come from the true Prophet (ﷺ), so when the time of Salat (prayer) comes one of you should announce the Adhan and the one of you who knows the Qur'an most should be your Imam." He ('Amr) said: "They looked around and there was no one who knew the Qur'an more than I. So they put me forward in front of them and I was only six or seven years old."

[Reported by al-Bukhari, Abu Dawud and an-Nasa'i].
وَعَنْ عَمْرِو بْنِ سَلَمَةَ قَالَ: قَالَ أَبِي: { جِئْتُكُمْ مِنْ عِنْدِ اَلنَّبِيِّ ‏- صلى الله عليه وسلم ‏-حَقًّا.‏ قَالَ: 
"فَإِذَا حَضَرَتْ اَلصَّلَاةُ فَلْيُؤَذِّنْ أَحَدُكُمْ, وَلْيَؤُمَّكُمْ أَكْثَرُكُمْ قُرْآنًا", قَالَ: فَنَظَرُوا فَلَمْ يَكُنْ أَحَدٌ أَكْثَرَ قُرْآنًا مِنِّي, فَقَدَّمُونِي, وَأَنَا اِبْنُ سِتٍّ أَوْ سَبْعِ سِنِينَ }  رَوَاهُ اَلْبُخَارِيُّ, وَأَبُو دَاوُدَ, وَالنَّسَائِيّ ُ  1‏ .‏‏1 ‏- صحيح.‏ رواه البخاري (4302)‏، وأبو داود (585، والنسائي (2/80‏-81)‏ واللفظ للبخاري من حديث طويل.‏