‘Abd ar-Rahman b Sa'd b. 'Ammar b. Sa‘d, the mu’adhdhin* of Allah's Messenger ﷺ, said that his father told him from his father from his grandfather that Allah's Messenger ﷺ commanded Bilal to put his fingers in his ears, saying that it made the voice louder. * The mu’adhdhin here mentioned was Sa‘d, great-grandfather of ‘Abd ar-Rahman. Ibn Majah transmitted it.