Musnad Ahmad 5:302

Ali ibn Bahr narrated to us, Isa ibn Yunus narrated to us, Zakariya narrated to us, from Abu Ishaq, from Hani ibn Hani, from Ali, who said: Abu Bakr used to lower his voice when he recited, and Umar used to raise his voice in his recitation, and Ammar, when he recited, would take from this surah and that one. That was mentioned to the Prophet, peace and blessings of Allah be upon him. He said to Abu Bakr: "Why do you lower your voice?" He said: "I make sure the One I am conversing with hears me." He said to Umar: "Why do you raise your voice in your recitation?" He said: "I frighten the devil and awaken the sleepy one." He said to Ammar: "And why do you take from this surah and that one?" He said: "Do you hear me mixing into it what is not from it?" He said: "No." He said: "Then all of it is good."