TIRMIDHI 725:
from ʿAbdullāh b. ʿĀmir b. Rabīʿah from his father —
"I saw the Prophet - (a number of times) such that I was not able to count - using the Siwak while he was fasting."
الترمذي ٧٢٥:
عن عبد الله بن عامر بن ربيعه عن أبيه —
رَأَيْتُ النَّبِيَّ ﷺ مَا لاَ أُحْصِي يَتَسَوَّكُ وَهُوَ صَائِمٌ قَالَ وَفِي الْبَابِ عَنْ عَائِشَةَ