The Messenger of Allah ﷺ was using the tooth-stick, when two men, one older than the other, were with him. A revelation came to him about the merit of using the tooth-stick. He was asked to show proper respect and give it to the elder of the two.  

كَانَ رَسُولُ اللَّهِ ﷺ يَسْتَنُّ وَعِنْدَهُ رَجُلاَنِ أَحَدُهُمَا أَكْبَرُ مِنَ الآخَرِ فَأُوحِيَ إِلَيْهِ فِي فَضْلِ السِّوَاكِ أَنْ كَبِّرْ أَعْطِ السِّوَاكَ أَكْبَرَهُمَا قَالَ أَحْمَدُ هُوَ ابْنُ حَزْمٍ قَالَ لَنَا أَبُو سَعِيدٍ هُوَ ابْنُ الأَعْرَابِيِّ هَذَا مِمَّا تَفَرَّدَ بِهِ أَهْلُ الْمَدِينَةِ  

"What would the Messenger of Allah ﷺ do as soon as he entered the house?" She replied: "(He would use) the siwak."  

قُلْتُ لِعَائِشَةَ بِأَىِّ شَىْءٍ كَانَ يَبْدَأُ رَسُولُ اللَّهِ ﷺ إِذَا دَخَلَ بَيْتَهُ قَالَتْ بِالسِّوَاكِ