أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ مُحَمَّدِ بْنِ زِيَادٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ مُحَمَّدٌ صلى الله عليه وسلم ‏"‏ أَلاَ يَخْشَى الَّذِي يَرْفَعُ رَأْسَهُ قَبْلَ الإِمَامِ أَنْ يُحَوِّلَ اللَّهُ رَأْسَهُ رَأْسَ حِمَارٍ ‏"‏ ‏.‏

It was narrated that Abu Hurairah said: "Muhammad (PBUH) said: 'Does the one who raises his head before the Imam not fear that Allah may turn his head into the head of a donkey?"' Translation Not Available

Book Ref: Sunan An Nisai Book 10 Hadith 828
Web Ref:  Sunan An Nisai Vol 1 Book 10 Hadith 829