Volume 7 · Book 61 · Hadith 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."
— Sahih Bukhari, Volume 7, Book 61: Virtues of the Qur'an, Hadith #541