Bara reported, and he was not one to lie, that whenever they prayed with the Messenger of Allah ﷺ and he raised his head from the bowing position, they would remain standing until they saw him prostrate, and only then would they prostrate.
أخبرنا يعقوب بن إبراهيم قال حدثنا ابن علية قال أنبأنا شعبة عن أبي إسحق قال سمعت
حدثنا البراء وكان غير كذوب أنهم كانوا إذا صلوا مع رسول الله ﷺ فرفع رأسه من الركوع قاموا قياما حتى يروه ساجدا ثم سجدوا
Bukhari transmitted it in the Book of the Adhan, chapter on raising the eyes toward the imam during prayer, h: 747, from the hadith of Shubah, and Muslim in the Book of Prayer, chapter on following the imam and acting after him, h: 474, from the hadith of Abu Ishaq Sabi through the same route, and it is in Kubra, h: 903.