Abu Hazim al-Tammar narrates from al-Bayadi (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) came out to the people while they were praying, and their voices had become loud with recitation. He (peace and blessings be upon him) said: "The one who prays is conversing intimately with his Lord, so let him consider what he is saying to Him in that intimate conversation; and do not raise your recitation over one another."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4704