The Messenger of Allah ﷺ was using a tooth-stick while two men were with him, one older than the other. Allah revealed to him concerning the merit of the tooth-stick, "Give precedence to the elder. Hand the tooth-stick to the older of the two first."
كان رسول الله ﷺ يستن، وعنده رجلان أحدهما أكبر من الآخر، فأوحى الله إليه في فضل السواك: أن كبر: أعط السواك أكبرهما.
Abu Dawud narrated it (50), saying, "Muhammad bin Isa told us, Anbasah bin Abdul-Wahid told us, from Hisham bin Urwa, from his father, from Ayesha," and he related the hadith. Its isnad is hasan because of Muhammad bin Isa bin Qasim bin Sumay (in the diminutive form), concerning whom there is disagreement, though his hadith is hasan. Hafiz also graded it hasan in Fath [Bari] (1/357).Abu Dawud said, Ahmad bin Hazm said, Abu Saeed, who is al-Arabi, said, "This is something transmitted only by the people of Madinah."His saying "yastann" means he brushes his teeth. Its root is taken from "sinn" (tooth), which refers to passing something rough over something else. From this comes "misan," the whetstone used to sharpen iron and similar things. He means that he used to rub his teeth.