Jabir said :

when the prophet (ﷺ) became seriously ill, we prayed behind him while he was sitting and Abu Bakr was calling “Allah is most great “ to cause the people to hear the TAKBIR. Then he (the narrators) narrated the rest of the tradition.

حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، وَيَزِيدُ بْنُ خَالِدِ بْنِ مَوْهَبٍ، - الْمَعْنَى - أَنَّ اللَّيْثَ، حَدَّثَهُمْ عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، قَالَ اشْتَكَى النَّبِيُّ صلى الله عليه وسلم فَصَلَّيْنَا وَرَاءَهُ وَهُوَ قَاعِدٌ وَأَبُو بَكْرٍ يُكَبِّرُ لِيُسْمِعَ النَّاسَ تَكْبِيرَهُ ثُمَّ سَاقَ الْحَدِيثَ ‏.‏