Abu Hurairah reported the Messenger of Allah ﷺ as saying; Does he who raises his head while the Imam is prostrating not fear that Allah may change his head into a donkey’s or his face into a donkey’s face.  

قَالَ رَسُولُ اللَّهِ ﷺ أَمَا يَخْشَى أَوْ أَلاَ يَخْشَى أَحَدُكُمْ إِذَا رَفَعَ رَأْسَهُ وَالإِمَامُ سَاجِدٌ أَنْ يُحَوِّلَ اللَّهُ رَأْسَهُ رَأْسَ حِمَارٍ أَوْ صُورَتَهُ صُورَةَ حِمَارٍ