Isma'il bin Ubayd bin Rifa'ah narrates from his father that when Sayyiduna Mu'awiyah (may Allah be pleased with him) came to Madinah, he led them in prayer, but he did not recite 'Bismillah al-Rahman al-Rahim' (In the name of Allah, the Most Gracious, the Most Merciful), nor did he say the takbir when going down and when rising. When he concluded with the salam, the Muhajirun and the Ansar called out to him: O Mu'awiyah! You have stolen from your prayer! Where is Bismillah al-Rahman al-Rahim? And where is the takbir when you go down and when you rise?
So he led them in prayer again, and in it he did the things for which they had faulted him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2410