19 – This hadith does not explicitly state whether rinsing the mouth and sniffing water into the nose are to be done with a single handful of water or with more. One may infer the first, because it mentions repeating the washing of the face and the forearms yet leaves the taking of water for the mouth and nose unrestricted; moreover, the hadith of ʿAbd Allāh b. Zayd shows that both acts are performed with one handful.

21 – Blowing the water out of the nose is done with the left hand; nothing in the hadith indicates the use of the right.

22 – It is permissible to ask someone else to bring the water for purification.

23 – The very root of the word for rinsing the mouth (madmadah) conveys movement, which implies swishing the water around inside the mouth.

Scholarly disagreement
The three imams—Mālik, al-Shāfiʿī, and Abū Ḥanīfah—together with Sufyān and others, hold that rinsing the mouth and nose is not obligatory but merely recommended. Their evidence is the hadith, “Ten practices belong to the natural disposition …,” reported by Muslim (261), among which is inhaling water into the nose; and, they argue, a sunnah is not obligatory. This proof is very weak, for sunnah in the hadith means “way” or “manner,” not the later technical sense of an act whose performer is rewarded and whose neglecter is not punished.

They also cite the verse in Sūrat al-Māʾidah, but that reasoning is questionable, for the mouth and nose are included in what the Qur’an calls the face.

Imām Aḥmad, however, considers rinsing the mouth and nose obligatory; so do Ibn Abī Laylā, Isḥāq, and others.

Those who impose the obligation advance several proofs, among them:
First: The Prophet ﷺ consistently performed these two acts and never omitted them, which shows that they are compulsory. Had they been only recommended, he would have left them out at least once to demonstrate permissibility. Moreover, an action coupled with a divine command indicates obligation, and Allah has commanded them when He says, “So wash your faces” (5:6); the mouth and nose fall within the boundaries of the face.