Is it permissible to make an exception from an exception?
Chapter on Explicit Divorce and Others
Al-Mughni
Book of Divorce
Primary text
Making an exception from an exception is valid. This principle applies generally, but its application in divorce (Talaq) is restricted, with scholarly difference regarding the statement: 'You are divorced three times, except for two, except for one.' If we permit the exception of half (two out of three), then two divorces occur. The justification for permitting the exception of two from three, even though two is the majority, is that the speaker did not stop there but followed it by excepting one from those two, making the statement equivalent to one divorce. The exception in all these cases must be contiguous with the statement of affirmation.
Supporting text
The view that the initial exception is nullified because it is an exception of the entirety, rendering the subsequent 'except for one' to apply to the established three, resulting in two divorces, is considered secondary. The primary view rejects this because excepting from a negation is affirmation, and excepting from an affirmation is negation; therefore, excepting one from the negated two would be affirming them, which cannot be made to apply to the established three as that would be affirming from affirmation.