"I came to the Messenger of Allah in Abtah, when he was in a red tent. Bilal came out and gave the call to prayer, turning around and putting his fingers in his ears."
Sunan Ibn Majah Book 3, Hadith 6
← Previous Hadith The Messenger of Allah commanded Bilal to put his fingers in his ears when calling the Adhan, and he said: "It makes the voice louder."

Sunan Ibn Majah Book 3, Hadith 5 Next Hadith → "The Messenger of Allah said: There are two characteristics in which the Muslims are dependent upon their Mu'adh-dhins: their prayer and their fasting."

Sunan Ibn Majah Book 3, Hadith 7