The fifth condition: being free of impediments. This applies specifically to women. A menstruating woman is not required to fast, nor is a woman experiencing postnatal bleeding, for the Prophet, peace and blessings be upon him, affirmed this when he said: “Is it not the case that when she menstruates, she neither prays nor fasts?” (1) By consensus, fasting is neither obligatory for her nor valid from her; and by consensus, she must make it up. Thus, there are three points of consensus. A woman experiencing postnatal bleeding is like a menstruating woman in this regard.
If confirmation is established during the day, abstaining and making up the fast become obligatory upon everyone who becomes subject to its obligation during that day ........
His statement: “If confirmation is established during the day, abstaining and making up the fast become obligatory upon everyone who becomes subject to its obligation during that day.” Confirmation here means confirmation that the month has begun, either through testimony or by completing thirty days of Sha'ban. His statement, “abstaining becomes obligatory,” means abstaining from that which invalidates the fast.
The evidence for this is that when the Prophet, peace and blessings be upon him, instructed the people to fast on Ashura during the course of the day, they immediately abstained (2). Moreover, once it was established that this day was part of Ramadan, abstaining for the rest of it became obligatory.
His statement, “and making up the fast,” means that they must make up that day during which confirmation was established that it was part of Ramadan. The reason is that one condition for the validity of an obligatory fast is that the intention encompass the entire day—that it be made before dawn. Here, however, the intention was formed during the day, so they had not fasted a complete day. The Prophet, peace and blessings be upon him, said: “Actions are only by intentions, and every person shall have only what he intended.” (3)