Assalamu alaikum wa rehmatullahi wa barakatuh
Narrated Abu Huraira:
The Prophet said, “If anyone of you rouses from sleep and performs the ablution, he should wash his nose by putting water in it and then blowing it out thrice, because Satan has stayed in the upper part of his nose all the night.” (Sahih al-Bukhari, Volume 4, Book 54, Number 516)
Shaitan is Jinn made of smoke,or some sort of gases.It’s invisibility also suggests it.
During sleep,the intake of air and its excretion (inhalation and exhalation) are disturbed in some pathological cases and these processes are also even moderated in normal cases such as the nasal cycle.Some of the cases are mentioned below.
First of all,there are many sleep disorders caused due to abnormal breathing known as Sleep disordered breathing.Some of them are listed below.
Snoring is a result of the changes in the configuration and properties of the upper airway (from the nasopharynx to the laryngopharynx) that occurs during sleep.
Snoring is a sign of abnormal breathing. It occurs when physical obstruction causes fluttering of the soft palate and the adjacent soft tissues between the mouth, external orifices of the nose (nares), the upper part of the windpipe (trachea), and the passage extending from the pharynx to the stomach (esophagus).
2.Obstructive sleep apnea hypopnea syndrome:
OSAHS is characterized by recurrent episodes of partial or complete airway obstruction during sleep due to repetitive obstruction of the upper airway, necessitating recurrent awakenings or arousals to re-establish airway patency, often with oxygen desaturation
Secondly,the nasal cycle is prolonged during sleep,and it is actually the physiological /normal type of congestion.Wudu or ablution actually helps in decongestion.This is a list of home remedies for pathological congestion which includes passing water into the nose at the first place.
So again,whatever Our Holy Prophet Muhammad s.a.w.w. has told,is absolutely correct.He s.a.w.w. was truly guided by Allah and What ever Our Allah has taught us is 100% correct and it is only for our own Benefit.THANKS TO ALLAH.