It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Does the one who raises his head before the imam not fear that Allah will turn his head into the head of a donkey?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2599
Muhammad bin Ziyad said: I heard Sayyiduna Abu Hurayrah (may Allah be pleased with him) say: I heard Abu al-Qasim (peace and blessings be upon him) say: "Does the one who raises his head before the imam not fear that Allah Almighty will turn his head into that of a donkey?"
Shu'bah said in his narration: "Or (turn) his form into the form of a donkey."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2600
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Does any one of you not fear that, for raising his head from prostration before the imam, Allah Almighty will change his head into the head of a donkey?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2601
(a) Al-Harith bin Makhlad reports from his father that he heard Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) say: When one of you raises his head from prostration before the imam, thinking that the imam has risen, let him go back into prostration. Then, when the imam raises his head from prostration, let him remain for as long as he had left off before.
(b) It is reported from Ibrahim al-Nakha'i and al-Sha'bi (may Allah have mercy on them both) that he should go back and prostrate.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2602