What is the ruling on expiation for one who swore to abandon masturbation by fasting, then slipped and repeated the act with an increased fasting period? Is there one expiation for all acts or two expiations? And is it permissible to suffice with the initial fasting along with the expiation, rather than the additional fasting?

If a fast is vowed for a single thing, then what is obligatory is either to fulfill the vow and fast the vowed days, or to offer a single expiation for both vows. The expiation is repeated with the repetition of breaking the oath, because the phrase "every time" (كلما) entails repetition. Repentance is obligatory for the mentioned habit, along with the firm intention not to return to it.