Is expiation obligatory for one who has intercourse with his wife at the beginning of her menstruation, being ignorant of its prohibition and thinking it to be merely disliked? What is this expiation, and what should he do if he is unable to offer it?

Placing a barrier, such as a condom, does not permit intercourse with a menstruating woman, nor does it waive the expiation (kaffara) for those who deem it obligatory. There is a disagreement regarding the obligation of expiation for having intercourse with a menstruating woman: the majority of scholars do not obligate it upon one who is ignorant or has repented, while the Hanbalis obligate it even upon the ignorant, and it is waived if one is unable to fulfill it. The expiation, where it is obligatory, is one dinar or half a dinar (approximately 4.25 grams of pure gold). The fatwa obligates the expiation upon you and your wife if she complied, and it is waived if one is unable to fulfill it.