If it is asked: What is the wisdom behind forbidding one who rises from sleep to immerse his hand before washing it three times?
The answer is that the Prophet, peace and blessings be upon him, explained the wisdom in his words: “For one of you does not know where his hand spent the night.”
If someone says: “I placed my hand in a bag, so I know that it did not touch anything impure from my body. Moreover, I went to sleep after performing a legislated cleansing, and even if it were assumed that it touched the penis or the anus, it would not become impure.”
The answer is that the jurists, may Allah have mercy on them, said: The effective cause is unknown, so acting upon this falls under the category of purely devotional observance (1).
However, the apparent meaning of the hadith is that the ruling is explained by his words: “For one of you does not know where his hand spent the night.”
Shaykh al-Islam, may Allah have mercy on him, mentioned that this explanation is like the Prophet’s explanation in his words: “When one of you awakens from sleep, let him blow his nose three times, for Satan spends the night upon the upper passages of his nose” (2). It is therefore possible that Satan may have tampered with this hand, bringing to it things harmful to a person or contaminating to the water. Thus, the Prophet, peace and blessings be upon him, forbade him from immersing his hand until he had washed it three times (3).
What the Shaykh, may Allah have mercy on him, mentioned is sound. Otherwise, if we were to return to the command