They used to pray behind the Messenger of Allah ﷺ. When he raised his head from bowing, I would not see anyone bend his back until the Messenger of Allah ﷺ placed his forehead on the ground. Then those behind him would fall down in prostration.In another narration, "When he bowed, they bowed. When he raised his head from bowing and said, 'Allah hears whoever praises Him,' we would remain standing until we saw that he had placed his face on the ground, then we would follow him."In another narration, "We were with the Prophet ﷺ. Not one of us would bend his back until we saw that he had prostrated."
إنهم كانوا يصلون خلف رسول الله ﷺ فإذا رفع رأسه من الركوع لم أر أحدا يحني ظهره حتى يضع رسول الله ﷺ جبهته على الأرض. ثم يخر من وراءه سجدا. وفي رواية: فإذا ركع ركعوا، وإذا رفع رأسه من الركوع فقال: سمع الله لمن حمده لم نزل قياما حتى نراه قد وضع وجهه في سمع الأرض، ثم نتبعه. وفي رواية: كنا مع النبي ﷺ: لا يحنو أحد منا ظهره حتى نراه قد سجد.
Bukhari narrated it in "Adhan" (690), and Muslim narrated it in "Prayer" (474), both through the route of Abu Ishaq, who said, Abdullah bin Yazid narrated to me, who said, Bara narrated to me, and he was no liar.The second narration was reported by Muslim through the route of Muharib bin Dithar, who said, I heard Abdullah bin Yazid say on the pulpit, Bara narrated to us that they used to pray with the Messenger of Allah ﷺ, then he mentioned something similar.The third narration was reported through the route of Hakam, from Abdul-Rahman bin Abu Layla, from Bara, with the same wording.