Musnad Ahmad #822

It was narrated that ‘Ali (رضي الله عنه) said: Abu Bakr (رضي الله عنه) used to recite in a low voice when he recited, and ‘Umar (رضي الله عنه) recited in a loud voice. When `Ammar (رضي الله عنه) recited, he would recite some from one soorah and some from another. That was mentioned to the Prophet (ﷺ) and he said to Abu Bakr (رضي الله عنه); `Why do you recite in a low voice?` He said: Because the One with Whom I am conversing can hear. He said to ʼUmar (رضي الله عنه): “why do you recite out loud?” He said: To scare the Shaitan and awaken those who are asleep. He said to ‘Ammar (رضي الله عنه): “Why do you recite some from one soorah and some from another?` He said: Do you hear me mixing with it something that is not part of it? He said: `No.` Then he said: `All of it is good.”