Abu Dawud
Prayer
Book Number: 002 / Hadith Number: 1327
Narated By Abu Sa'id al-Khudri : The Apostle of Allah (pbuh) retired to the mosque. He heard them (the people) reciting the Qur'an in a loud voice. He removed the curtain and said: Lo! every one of you is calling his Lord quietly. One should not trouble the other and one should not raise the voice in recitation or in prayer over the voice of the other.