السواك
A twig from the arak (Salvadora persica) tree, chewed and brushed against the teeth and gums as a recommended daily — even pre-prayer — hygiene practice.
لَوْلَا أَنْ أَشُقَّ عَلَى أُمَّتِي لَأَمَرْتُهُمْ بِالسِّوَاكِ عِنْدَ كُلِّ صَلَاةٍ
“Were it not that it would be difficult for my community, I would have commanded them to use the tooth-stick before every prayer.” (meaning, not a literal translation)
'A'ishah reported he would begin with the miswak on entering his home, and would clean his mouth with it on waking at night (Sahih Muslim; Sunan an-Nasa'i). The phrasing "were it not that it would be difficult" is notable — it explicitly frames miswak use as something the Prophet ﷺ considered stopping short of making obligatory specifically out of concern for placing hardship on the community, rather than any doubt about its benefit.
Ibn al-Qayyim and later dental researchers alike note the arak twig's natural antibacterial compounds; the practice is now studied as an early precedent for regular mechanical tooth-cleaning. He describes the practice as beneficial beyond the mouth itself — sharpening mental clarity and pleasing to Allah, in addition to its more obviously physical dental benefit — reflecting how Prophetic-medicine texts often frame a single practice as serving both spiritual and bodily purposes together.
Dental research has studied Salvadora persica (arak/miswak) specifically, finding it contains compounds with genuine antibacterial and plaque-reducing properties, and the World Health Organization has previously noted miswak as an effective oral hygiene tool. Noted here as separate modern research context supporting the practice's physical benefit, alongside — not replacing — the spiritual dimension the hadith itself emphasizes.