Sahih al-Bukhari · #244
حَدَّثَنَا أَبُو النُّعْمَانِ، قَالَ حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، عَنْ غَيْلاَنَ بْنِ جَرِيرٍ، عَنْ أَبِي بُرْدَةَ، عَنْ أَبِيهِ، قَالَ أَتَيْتُ النَّبِيَّ صلى الله عليه وسلم فَوَجَدْتُهُ يَسْتَنُّ بِسِوَاكٍ بِيَدِهِ يَقُولُ " أُعْ أُعْ "، وَالسِّوَاكُ فِي فِيهِ، كَأَنَّهُ يَتَهَوَّعُ.
English
Narrated Abu Burda:My father said, "I came to the Prophet (ﷺ) and saw him carrying a Siwak in his hand and cleansing his teeth, saying, 'U' U'," as if he was retching while the Siwak was in his mouth