Call to Prayers (Adhaan)

Bukhari :: Book 1 :: Volume 11 :: Hadith 658

Narrated Al-Bara:

(and he was not a liar) When Allah's Apostle said, "Sami a-l-lahu Liman hamida " none of us bent his back (for prostrations) till the Prophet prostrated and then we would prostrate after him.

Source materials are from the University of Southern California MSA site
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