What should one do who made two vows for two different matters, one of which was fulfilled but not the other, and he does not know which vow pertains to which matter?

You must remember what you vowed, for if it becomes clear to you or you strongly believe it, then you are obliged to fulfill it. If nothing becomes clear to you, some Shafi'i jurists believe that the entire vow must be fulfilled, while the majority hold that an expiation for an oath (kaffarat yameen) is required. This is because uncertainty about what was vowed is like not specifying it, and because the inability to define it is similar to someone who vows something and then becomes unable to fulfill it, based on the Prophet's (peace be upon him) saying: "The expiation for a vow that was not specified is the expiation for an oath."