QUESTION:  A person who sometime becomes insane and sometimes he seems in the state of sanity, so what would happen if this person divorces his wife?

Answer: If that person divorces his wife while he is in the state of insanity then his divorce will not take effect. On the other hand if he divorces while in the state of sanity then divorce will take effect in other words his wife will be divorced.

References: [1]Fatwa Shami vol-4:450/451 [2] Ahsanul Fatwa vol-5:130