Mukhtasar Bukhari (Abridged) 373 — Raising voice during adhan

Narrated Abu Sa'id Al-Khudri (may Allah be pleased with him): I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: "When you call the Adhan, raise your voice, for whoever hears the voice of the Mu'adhdhin, whether jinn, human, or anything else, will testify for him on the Day of Resurrection."