Abū ʿAlī al-Ḥāfiẓ > Abū ʿUbayd al-Qāsim b. Ismāʿīl > ʿUbaydullāh b. Saʿd from my uncle > Sayf b. Muḥammad > Yūnus b. al-Faḍl > Sālim b. ʿAbdullāh from his father

The cause of the death of Abu Bakr was the death of the Messenger of Allah ﷺ . His body continued to deteriorate until he died. Its chain of narration is weak.

حَدَّثَنِي أَبُو عَلِيٍّ الْحَافِظُ ثنا أَبُو عُبَيْدٍ الْقَاسِمُ بْنُ إِسْمَاعِيلَ حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ سَعْدٍ ثنا عَمِّي ثنا سَيْفُ بْنُ مُحَمَّدٍ عَنْ يُونُسَ بْنِ الْفَضْلِ عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ عَنْ أَبِيهِ قَالَ

«كَانَ سَبَبُ مَوْتِ أَبِي بَكْرٍ مَوْتَ رَسُولِ اللَّهِ ﷺ مَا زَالَ جِسْمُهُ يَجْرِي حَتَّى مَاتَ» إسناده واه