How can one perform ablution (wudu') with sinusitis and a deviated septum that causes complete blockage and prevents drawing water after scooping it?

Scholars have differed concerning the ruling on sniffing water into the nose (istinchāq). Some have deemed it obligatory, while others have considered it a Sunnah of ablution (wudūʾ). The latter is the view we favor. Therefore, the ablution of one who omits it despite being able to perform it is valid. And the ablution of one who is unable to perform it due to some ailment is valid a fortiori.