Is the prayer of one who wakes up, performs ablution (wudu') once—including the sniffing of water into the nostrils (istinshaq)—valid, given that it has been narrated that Satan spends the night in the nostrils, and given that it has been narrated that the Prophet performed ablution once and three times? And is the command here for obligation or for recommendation?

The hadith referred to in the Two Sahihs from Abu Hurayrah (may Allah be pleased with him) states: "When one of you wakes up from his sleep, he should blow his nose three times, for Satan spends the night in his nostrils." Some scholars have opined that this blowing of the nose (istinshar) is an independent Sunnah, unrelated to ablution (wudu'). However, the narration in Al-Bukhari qualifies it with ablution: "When one of you wakes up from his sleep and performs ablution, he should blow his nose three times." The majority of scholars understood the command in the hadith as a recommendation and a matter of preference (nadb and istihbab). Therefore, ablution is not invalidated by omitting the blowing of the nose, or by performing it once or twice, even though omitting it causes one to miss out on a great virtue. The majority of scholars based their view of it being a recommendation on the Prophet's (peace be upon him) statement to the Bedouin: "Perform ablution as Allah has commanded you," where he did not mention sniffing water into the nose (istinshaq) or blowing it out (istinthar). Furthermore, it is established that they were not mentioned in some descriptions of his (peace be upon him) ablution. As for the meaning of Satan spending the night in the nostrils, the hadith is understood literally; for the nose is one of the passages to the heart, and Satan enters through it. It may also be a metaphor, meaning that the filth that accumulates in the nostrils is in harmony with devils.