It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) performed i'tikaf and addressed the people, saying: "When one of you stands in prayer, he is speaking intimately with his Lord, so each of you should know what he is saying intimately to his Lord. And let none of you raise his voice over another in recitation during prayer."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13515