Sahih Bukhari Volume 2, Book 11, Hadith 891

حَدَّثَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنِي سُلَيْمَانُ بْنُ بِلاَلٍ، قَالَ قَالَ هِشَامُ بْنُ عُرْوَةَ أَخْبَرَنِي أَبِي، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتْ دَخَلَ عَبْدُ الرَّحْمَنِ بْنُ أَبِي بَكْرٍ، وَمَعَهُ سِوَاكٌ يَسْتَنُّ بِهِ، فَنَظَرَ إِلَيْهِ رَسُولُ اللَّهِ صلى الله عليه وسلم فَقُلْتُ لَهُ أَعْطِنِي هَذَا السِّوَاكَ يَا عَبْدَ الرَّحْمَنِ‏.‏ فَأَعْطَانِيهِ فَقَصَمْتُهُ ثُمَّ مَضَغْتُهُ، فَأَعْطَيْتُهُ رَسُولَ اللَّهِ صلى الله عليه وسلم فَاسْتَنَّ بِهِ وَهْوَ مُسْتَسْنِدٌ إِلَى صَدْرِي‏

Narrated By 'Aisha : AbdurRahman bin Abi Bakr came holding a Siwak with which he was cleaning his teeth. Allah's Apostle looked at him. I requested Abdur-Rahman to give the Siwak to me and after he gave it to me I divided it, chewed it and gave it to Allah's Apostle. Then he cleaned his teeth with it and (at that time) he was resting against my chest.