Sahih Bukhari
Virtues of the Quran
Volume: 006 / Book Number: 061 / Hadith Number: 541
Narrated Abu Huraira: Allah's Apostle said, "Allah does not listen to a prophet as He listens to a prophet who recites the Qur'an in a pleasant tone." The companion of the sub-narrator (Abu Salama) said, "It means, reciting it aloud."