Narrated Ibn Abu Mulaika: `Aisha said, "The Prophet (ﷺ) died in my house on the day of my turn while he was leaning on my chest closer to my neck, and Allah made my saliva mix with his Saliva." `Aisha added, "`AbdurRahman came with a Siwak and the Prophet (ﷺ) was too weak to use it so I took it, chewed it and then (gave it to him and he) cleaned his teeth with it."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا ابْنُ أَبِي مَرْيَمَ، حَدَّثَنَا نَافِعٌ، سَمِعْتُ ابْنَ أَبِي مُلَيْكَةَ، قَالَ قَالَتْ عَائِشَةُ ـ رضى الله عنها تُوُفِّيَ النَّبِيُّ صلى الله عليه وسلم فِي بَيْتِي، وَفِي نَوْبَتِي، وَبَيْنَ سَحْرِي وَنَحْرِي، وَجَمَعَ اللَّهُ بَيْنَ رِيقِي وَرِيقِهِ. قَالَتْ دَخَلَ عَبْدُ الرَّحْمَنِ بِسِوَاكٍ، فَضَعُفَ النَّبِيُّ صلى الله عليه وسلم عَنْهُ، فَأَخَذْتُهُ فَمَضَغْتُهُ ثُمَّ سَنَنْتُهُ بِهِ.
sunnah.com