عنْ أَبي هُريْرَةَ رَضِيَ اللّه عَنْهُ أَنَّ النَّبِيَّ صَلّى اللّهُ عَلَيْهِ وسَلَّم قَالَ: «أَمَا يَخْشَى أَحَدُكُمْ إِذا رفَعَ رأْسَهُ قَبْلَ الإِمَامِ أَنْ يَجْعلَ اللّه رأْسَهُ رأْسَ حِمارٍ، أَوْ يَجْعلَ اللّه صُورتَهُ صُورَةَ حِمارٍ» متفقٌ عليه.
Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (peace and blessings be upon him) said: "Does not any of you fear, when he raises his head before the imam, that Allah will turn his head into the head of a donkey, or that Allah will turn his form into the form of a donkey?" Agreed upon (al-Bukhari and Muslim).
الدروس · lessons
تحريم سبق الإمام بركن عملي كالركوع أو السجود أو القيام منهما ودليل التحريم أنّه توعد عليه بالمسخ وهو أشد العقوبات وتعتبر الصلاة صحيحة مع الإثم. حرمة من فعل ذلك عامدًا عالمًا بالحكم. مراعاة المتابعة للإمام في الصلاة من كمال الصلاة وأقربها قبولًا عند اللّه تعالى.
The prohibition of preceding the imam in a physical pillar [of the prayer] such as bowing, prostrating, or rising from them; the proof of prohibition is that a threat of disfigurement (maskh) is issued for it, which is among the severest of punishments—yet the prayer is still considered valid, albeit sinful. The sinfulness falls upon one who does that deliberately, knowing the ruling. Observing [proper] following of the imam in prayer is part of the perfection of the prayer and of what is nearest to being accepted by Allah, Exalted is He.