Ibn Abi Uways and Isa bin Mina both narrate: Abd al-Rahman bin Abi al-Zinad (may Allah have mercy on him) narrated to us from his father, and he narrates from the jurists of the people of Madinah that the imam's sutrah is itself the sutrah of those following him, whether they are few or many, and he bears their burden.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3885