What is the ruling on someone who committed masturbation during the daytime in Ramadan and does not remember the exact day, knowing that his fast was invalidated? Is expiation (kaffara) obligatory for him, and what is its amount and how is it calculated?

Whoever masturbates during the daytime in Ramadan is sinful and must make up the days he did so before the next Ramadan. If he delays making them up without a valid excuse, he must, in addition to making them up, pay an expiation for delaying for each day. If the questioner fasts the days he invalidated before the next Ramadan, then he owes nothing but repentance. If he does not fast, then he must make up the days he invalidated, and if the delay in making up repeats for several Ramadans, the expiation does not repeat; rather, he expiates for each day he delayed making up with a single expiation.