Arabic (Original)
وَبِإِسْنَادِهِ سَمِعْتُ أَبَا الْقَاسِمِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ أَمَا يَخْشَى أَحَدُكُمْ إِذَا رَفَعَ رَأْسَهُ وَالْإِمَامُ سَاجِدٌ أَنْ يَجْعَلَ اللَّهُ تَعَالَى رَأْسَهُ رَأْسَ حِمَارٍ.
English Translation
And with his chain: I heard Abu al-Qasim (peace and blessings be upon him) say: 'Does one of you not fear that, if he raises his head while the imam is still prostrating, Allah the Exalted might turn his head into the head of a donkey?'