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."
أَتَيْتُ النَّبِيَّ ﷺ فَوَجَدْتُهُ يَسْتَنُّ بِسِوَاكٍ بِيَدِهِ يَقُولُ أُعْ أُعْ وَالسِّوَاكُ فِي فِيهِ كَأَنَّهُ يَتَهَوَّعُ