until he has washed it three times, for none of you knows where his hand spent the night.” (1)

His statement, “from a night’s sleep,” excludes daytime sleep; washing the hands after it is not obligatory.

If someone were to say: In the hadith, the Prophet, peace and blessings be upon him, said, “When one of you awakens from his sleep,” and the word “sleep” is a singular noun annexed to a pronoun, so it encompasses every kind of sleep.

Moreover, the phrase “when he awakens” is a temporal expression that includes both the hours of night and the hours of day. Why, then, is it restricted to the night?

They answered: It is restricted to the night because of the Prophet’s reasoning in his statement, “For none of you knows where his hand spent the night,” since spending the night can only occur at night. (2) This is an instance of restricting a general expression by its underlying reason: when he, peace and blessings be upon him, gave a reason that applies only to night sleep, what is intended by the general wording “from his sleep” is night sleep. Thus, it is a general expression intended in a particular sense.

That invalidates ablution, . . .

His statement, “that invalidates ablution,” excludes the case in which the sleep does not invalidate it.

According to the school’s position, sleep that invalidates ablution is every kind of sleep, except for a brief slumber while standing or sitting. (3) The sound view is that the criterion for whether sleep invalidates ablution is awareness: so long as a person remains aware of himself such that he would notice if he passed wind, his sleep does not invalidate his ablution. But if he would not be aware of himself were he to pass wind, then his sleep invalidates his ablution. (310)

This is what the jurists mentioned here when they said, “that invalidates ablution,”