Points derived from the hadith:

1. Cleaning the teeth with a moist siwak.
2. Trimming and preparing the siwak before use.
3. It is permissible to use another person’s siwak after it has been washed and cleaned.
4. One should act upon what is understood from another’s signs and gestures.
5. “The Highest Companion” are those referred to in Surat al-Nisa’: “those whom Allah has favored of the prophets, the truthful, the martyrs, and the righteous.”

Hadith 4
Abu Musa al-Ash‘ari — may Allah be pleased with him — said: “I came to the Prophet ﷺ while he was brushing his teeth with a moist siwak (1). The tip of the siwak was on his tongue and he was saying, ‘Uʿ, uʿ,’ while the siwak was still in his mouth, as though he were retching.”

Unfamiliar terms

1. “Uʿ, uʿ”: pronounced with ḍammah on the hamzah and a quiescent ‘ain; an imitation of the sound made by a person who is about to vomit. Its original form is “haʿ, haʿ,” but the initial letter has been replaced with a hamzah.
2. “As though he were retching”: al-tahawwuʿ means to vomit audibly.

Overall meaning
Abu Musa al-Ash‘ari relates that he entered upon the Prophet ﷺ while the Prophet was cleaning his teeth with a fresh, moist twig, because such a twig cleans more thoroughly and does not splinter in the mouth, which would cause discomfort. He had placed the siwak on his tongue and was brushing so vigorously that it appeared as though he were about to vomit.

Points derived from the hadith:

1. It is sunnah to use a fresh, moist twig for siwak, and the siwak itself is an act of worship and devotion.
2. Vigorous brushing is recommended, for thoroughness achieves complete cleanliness.
3. One should, on occasion, pass the siwak over the tongue as well.