What is the ruling on breaking an obligatory fast, such as make-up or vow fast, after starting?

Primary text

It is not permissible to exit an obligatory fast, whether it is the make-up of Ramadan, a specific or general vow, or a fast of expiation (Kaffarah). This is because a specifically designated obligation requires commitment upon entering, and an unspecified one becomes designated by commencing it, placing it in the position of a defined obligatory act. There is no difference of opinion on this matter.