Hawzah News Agency – Q: A person, responsible for performing an obligatory fast, decided to fulfill his duty but could not because of unforeseen circumstances. For example, he prepared to travel after sunrise — he traveled, but failed to return home before noon. He had not done anything that invalidates the fast, except that the time for making the intention of an obligatory fast has elapsed; and that day is one in which fasting is mustaḥabb. Is it valid if he makes the intention to perform a mustaḥabb fast?

A: When one is responsible for the qaḍā’ of Ramadan fast, it is invalid to make intentions to perform a mustaḥabb fast, even if the time for making intention for performing an obligatory fast has passed.

Source: https://www.leader.ir/en/book/32/Practical-Laws-of-Islam