Ruling on one who begins making up a fast and then wants to break it

Question:
Is it obligatory to complete the fast if the person fasting is making up days from Ramadan, then he desires to break his fast and make up this day with another day?

Answer:
What is known among the scholars is that if one has begun an obligatory act, he must complete it, and it is not permissible for him to break his fast except for a valid excuse, such as an illness that befalls him, or travel, or a state of ritual impurity. Otherwise, it is obligatory for him to complete the obligatory fast, such as making up Ramadan or fulfilling a vow; he must complete it and not break it except for an excuse that permits breaking the fast.