Musnad Abu Ya'la al-Mawsili 150:100

Dāwūd ibn ‘Amr al-Ḍabbī narrated to us, Nāfi‘ ibn ‘Umar al-Jumaḥī narrated to us, from Ibn Abī Mulaykah, who said: ‘Ā’ishah said: The Messenger of Allah (may Allah bless him and grant him peace) passed away in my house, on my day, and between my chest and my throat, and Allah joined my saliva with his saliva. ‘Ā’ishah said: ‘Abd al-Raḥmān ibn Abī Bakr entered with a siwāk, and the Prophet (may Allah bless him and grant him peace) became too weak for it, so I took it, chewed it, and then brushed him with it.