Sahih Bukhari Volume 6, Book 60, Hadith Number 246.

Narrated By Ibn Abbas : (Regarding): ‘Neither say

your, prayer aloud, nor say it in a low tone.’

(17.110) This Verse was revealed while Allah’s

Apostle was hiding himself in Mecca. When he prayed

with his companions, he used to raise his voice

with the recitation of Qur’an, and if the pagans

happened to hear him, they would abuse the Qur’an,

the One who revealed it and the one who brought it.

Therefore Allah said to His Prophet : ‘Neither say

your prayer aloud.’ (17.110) i.e. do not recite

aloud lest the pagans should hear you, but follow a

way between.