Muwatta Malik 176
موطأ مالك#176SahihYahya related to me from Malik from Yahya ibn Said from Muhammad ibn Ibrahim ibn al Harith at-Taymi from Abu Hazim at-Tammar from al Bayadi that the Messenger of Allah, may Allah bless him and grant him peace, came out to the people while they were praying and their voices were raised in the recitation. He said, "When you pray you are talking confidentially to your Lord. So look to what you confide to Him, and do not say the Qur'an out loud so that others hear it
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Salim al-HilaliSahih
In-book reference: 3:9