The Mother of the Believers, Sayyidah Aishah (may Allah be pleased with her), related the account of the illness of the Messenger of Allah (peace and blessings be upon him). She said: Abd al-Rahman bin Abi Bakr (may Allah be pleased with him) came in, and he had a siwak with him that he was using. the Messenger of Allah (peace and blessings be upon him) looked at him, so I said to him: "O Abd al-Rahman, give me this siwak." He gave it to me, then I chewed it, then I cleaned it, after which I gave it to the Messenger of Allah (peace and blessings be upon him). He (peace and blessings be upon him) used the siwak while he (peace and blessings be upon him) was reclining against my chest.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 170