From Sahih Bukhari (Hadith 3296):
Narrated `Abdur-Rahman bin `Abdullah bin `Abdur-Rahman bin Abi Sasaa Ansari:That Abu Sa`id Al-Khudri said to his father. "I see you are fond of sheep and the desert, so when you want to pronounce the Adhan, raise your voice with it for whoever will hear the Adhan whether a human being, or a Jinn, or anything else, will bear witness, in favor on the Day of Resurrection." Abu Sa`id added, "I have heard this from Allah's Messenger (ﷺ)
Reference: Bukhari 3296