It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The one who recites the Qur'an aloud is like the one who gives charity openly, and the one who recites the Qur'an quietly is like the one who gives charity secretly."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7711