Sunan Ibn Majah Book 5, Hadith 158

“The Prophet (ﷺ) used to teach us not to bow or prostrate before the Imam; when he says the Takbir then say the Takbir, and when he prostrates, you should prostrate.”

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“The Messenger of Allah (ﷺ) forbade performing prayer behind one who is engaged in conversation or one who is sleeping.”

Sunan Ibn Majah Book 5, Hadith 157
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“The Messenger of Allah (ﷺ) said: ‘Does not the one who raises his head before the Imam fear that Allah may turn his head into the head of a donkey?’”

Sunan Ibn Majah Book 5, Hadith 159