Musnad Ahmad 8156

Translation

✧ The imam is appointed only to be followed, so do not differ from him. When he says the takbir, say the takbir; when he bows, bow; when he says, 'Allah hears the one who praises Him,' say, 'O Allah, our Lord, to You belongs praise'; when he prostrates, prostrate; and when he prays sitting, then pray sitting, all of you.

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