It is narrated from Muharib bin Dithar: I heard Sayyiduna Abdullah bin Yazid (may Allah be pleased with him) say on the pulpit: Sayyiduna al-Bara' bin Azib (may Allah be pleased with him) narrated to us: We used to pray with the Messenger of Allah (peace and blessings be upon him). When he (peace and blessings be upon him) bowed, we bowed, and when he (peace and blessings be upon him) raised his head from bowing, he would say 'Sami'allahu liman hamidah' (Allah has heard the one who praised Him), and we would remain standing until we saw that he (peace and blessings be upon him) had placed his forehead on the ground; then we would go down for prostration.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2595