Chapter: When should those who are behind the Imam prostrate?

Hadith Number 690

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Narrated Al-Bara

(and he was not a liar) When Allah's Messenger (ﷺ) said, "Sami`a l-lahu liman hamidah" none of us bent his back (for prostration) till the Prophet (ﷺ) prostrated and then we would prostrate after him.