Abd al-Rahman bin Sa'd bin Ammar bin Sa'd narrates from his father, who narrates from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) ordered Bilal (may Allah be pleased with him): "Put your fingers in your ears." His iqamah, 'Qad qamatis-salah' (The prayer has begun), was said once.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1855