Awn bin Abi Juhayfah (may Allah have mercy on him) narrates from his father: I saw Sayyiduna Bilal (may Allah be pleased with him) giving the adhan; he had put his fingers in his ears and was turning right and left in his adhan.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1854