Sahih Bukhari 690

Narrated Abu Huraira: The Prophet said, Isn't he who raises his head before the Imam afraid that Allah may transform his head into that of a donkey or his figure (face) into that of a donkey? ..

Narrated Ibn `Umar: When the earliest emigrants came to Al-`Usba [??] a place in Quba', before the arrival of the Prophet- Salim, the slave of Abu Hudhaifa, who knew the Qur'an more than the others used to lead them in prayer. ..

Narrated Anas: The Prophet said, Listen and obey (your chief) even if an Ethiopian whose head is like a raisin were made your chief. ..

Narrated Abu Huraira: Allah's Apostle said, If the Imam leads the prayer correctly then he and you will receive the rewards but if he makes a mistake (in the prayer) then you will receive the reward for the prayer and the sin will be his. ..

Narrated 'Ubaid-Ullah bin Adi bin Khiyar: I went to 'Uthman bin Affan while he was besieged, and said to him, You are the chief of all Muslims in general and you see what has befallen you. We are led in the Salat (prayer) by a leader of Al-Fitan..

Narrated Anas bin Malik: The Prophet said to Abu-Dhar, Listen and obey (your chief) even if he is an Ethiopian with a head like a raisin. ..