Musannaf Ibn Abi Shaybah

Hazrat Mujahid heard a man raising his voice in supplication, so he threw a pebble at him.

Hazrat Ibn Umar (may Allah be pleased with them both) regarding raising the voice in du'a says that you are not calling upon one who is deaf or far away.

Hazrat Anas and Hasan considered it undesirable that a person's supplication be heard by the person sitting with him.

Hasan says that the predecessors used to supplicate abundantly, but only a humming sound of their voices could be heard.

It is narrated from Hazrat Ibn Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: When a person performs prayer, he is conversing with his Lord, so each of you should know whom he is conversing with. Therefore, do not raise your voice in prayer as you do in mutual conversation among yourselves.

Hazrat Abu Musa narrates that we were on a journey with the Holy Prophet (peace and blessings be upon him), and people began to say Takbeer in loud voices. The Prophet (peace and blessings be upon him) said to them, "O people! Be kind to yourselves. You are not calling upon one who is deaf or distant, but upon One who hears and is near; He is with you; He is with you."

Hazrat Abdullah bin Naseeb narrates that I performed the Maghrib prayer with Hazrat Saeed bin Musayyib. When I sat in the second rak'ah, I raised my voice in dua, and he rebuked me for it. When I completed the prayer, I asked him, "Which of my actions did you dislike?" He replied, "Do you think that Allah is not near to you?"