The Prophet ﷺ 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?" (Using translation from Bukhārī 691)
قَالَ رَسُولُ اللَّهِ ﷺ «أَمَا يَخْشَى أَحَدُكُمْ أَوْ أَلَا يَخْشَى أَحَدُكُمْ إِذَا رَفَعَ رَأْسَهُ قَبْلَ الْإِمَامِ أَنْ يَجْعَلَ اللَّهُ رَأْسَهُ رَأْسَ حِمَارٍ أَوْ صُورَتَهُ صُورَةَ حِمَارٍ؟ »