What is the ruling on someone who vowed to fast three days for every time they committed a specific sin, and they have committed it 66 times? Are they obligated to fast 198 days? Can they annul the vow after expiation before the specified period ends? Do they expiate for each act separately or is one expiation sufficient for all acts? Is it permissible to feed ten poor persons the equivalent of one and a half kilograms of the staple food of the country for each poor person?

Whoever made a vow contingent on committing a forbidden act, with the intention of abandoning it, is given a choice between fulfilling their vow or offering an expiation for an oath (kaffarat yamin (definition)). This is what the Hanafis and Shafi'is have explicitly stated. Therefore, you are not obligated to fulfill this vow, but you are given a choice between fulfilling it and offering an expiation for an oath. Whichever you choose to do will suffice. The obligation of the vowed act recurs with the recurrence of the action because it was made contingent with the word "every," meaning every time you commit the sin, you have a choice between fulfilling your vow and offering an expiation for an oath, knowing that you cannot cancel this vow before its specified duration ends.