It is narrated from Sayyiduna Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to order Sayyiduna Bilal (may Allah be pleased with him) to call the adhan slowly and deliberately and the iqamah quickly.
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Umar bin Bashir except Abu Mu'awiyah, and it is narrated from Sayyiduna Ali (may Allah be pleased with him) only with this chain."
This is how it is in the Dar al-Haramayn edition, whereas in Tarikh Asbahan it is (Mus'ad bin Alqamah) and in al-Daraqutni (Suwayd bin Ghafalah); and Allah knows best.
Hadith Referenceالمعجم الأوسط / باب الميم / 5030
Hadith Takhrij«أخرجه الدارقطني فى «سننه» برقم: 915»