´Al-Bara said:` "When we performed Salat behind Allah's Messenger, he would raise his head from bowing, and no man among us would bend his back until Allah's Messenger prostrated, then we prostrated."
Hadith Referenceسنن ترمذي / كتاب الصلاة / 281
Hadith Gradingالألبانی:صحيح، صحيح أبي داود (631 - 633)