The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 838
A'mash reported: When the Messenger of Allah (may peace be upon him) suffered from illness of which he died, and in the hadith transmitted by Ibn Mus-hir, the words are: The Messenger of Allah (may peace be upon him) was brought till he was seated by his (Abu Bakr's) side and the Apostle (may peace be upon him) led the people in prayer and Abu Bakr was making takbir audible to them, and in the hadith transmitted by 'Isa the (words are):" The Messenger of Allah (may peace be upon him) sat and led the people in prayer and Abu Bakr was by his side and he was making (takbir) audible to the people."