الاستنشاق والاستنثار
Drawing water into the nostrils and expelling it as a required part of ritual ablution, performed multiple times daily.
إِذَا تَوَضَّأَ أَحَدُكُمْ فَلْيَجْعَلْ فِي أَنْفِهِ مَاءً، ثُمَّ لِيَنْتَثِرْ
“When one of you performs ablution, let him draw water into his nose and then expel it.” (meaning, not a literal translation)
Because ablution (wudu) is performed at least five times daily before each prayer, this practice repeats far more often than most other hygiene instructions in the hadith corpus — a related narration (Sunan Abi Dawud 142) instructs performing it "vigorously" unless fasting, when a gentler approach is recommended to avoid accidentally swallowing water.
Commentators note the practical hygiene value of regularly clearing the nasal passage, a practice modern otolaryngology recognizes in saline nasal irrigation. Ibn al-Qayyim discusses this alongside the broader ablution ritual as serving both spiritual purification and genuine physical benefit simultaneously — a pattern that recurs across several of the hygiene-related practices covered on this site.
Saline nasal irrigation is a well-established modern practice recommended by many physicians for clearing allergens, mucus, and irritants from nasal passages, and some research has drawn direct comparisons between it and this specific ablution practice given the mechanical similarity.