Sayyiduna Anas (may Allah be pleased with him) says: Bilal (may Allah be pleased with him) was commanded to say the adhan in pairs and the iqamah in singles.

Sayyiduna Sa’d (may Allah be pleased with him) reports: The Prophet (peace and blessings be upon him) instructed Sayyiduna Bilal (may Allah be pleased with him) that when he gives the adhan, he should place his fingers in his ears, and said:“This will raise your voice.”

With this same chain, it is narrated that Sayyiduna Bilal (may Allah be pleased with him) would say the words of the adhan in pairs and would recite the testimony (tashahhud) twice. When he faced the qiblah, he would say:“Ashhadu an la ilaha illallah”twice.“Ashhadu anna Muhammadan Rasulullah”twice. Then he would repeat and say, while still facing the qiblah:“Ashhadu an la ilaha illallah”twice,“Ashhadu anna Muhammadan Rasulullah”twice. Then, turning to the right, he would say:“Hayya ‘ala-s-salah”twice. Then, turning to the left, he would say:“Hayya ‘ala-l-falah”twice. Then, still facing the qiblah, he would say:“Allahu Akbar, Allahu Akbar, la ilaha illallah.”His (may Allah be pleased with him) iqamah was unique; he would say“Qad qamatis salah”once. And on the day of Jumu’ah, the adhan for Jumu’ah during the time of the Messenger of Allah (peace and blessings be upon him) would be given when the shadow became equal to the strap.