From Sahih Muslim (Hadith 929):
Jabir said:The Messenger of Allah (ﷺ) led the prayer and Abu Bakr was behind him. When the Messenger of Allah (ﷺ) recited the takbir, Abu Bakr also recited (it) in order to make it audible to us. And the rest of the hadith is like one transmitted by Laith
Reference: Muslim 929