Is it obligatory for a menstruating woman to abstain if she becomes pure during the day?

The questioner : A questioner says: You referred to the disagreement regarding whether a menstruating woman or a woman with post-natal bleeding who becomes pure during the day must abstain. Is there a valid hadith in which the Messenger of Allah (peace and blessings be upon him), when he made fasting on the Day of Ashura obligatory, ordered those who had eaten after dawn to abstain? Is this evidence valid?

The Shaykh : This is, in fact, a question directed to students of knowledge, because perhaps only students of knowledge would understand it. There is no harm in explaining it. We mentioned during our discussion of fasting that if a woman is menstruating and becomes pure during the day, the scholars differed on whether she is required to abstain for the rest of the day, meaning she does not eat or drink, or whether it is permissible for her to eat and drink for the rest of the day.
We said that there are two narrations from Imam Ahmad regarding this. The first, which is the well-known position in the school, is that she is required to abstain and not eat or drink. The second is that she is not required to abstain, so it is permissible for her to eat and drink. We said that this second position is the school of Malik and al-Shafi'i, and it is also what is narrated from Ibn Mas'ud (may Allah be pleased with him), for he said: "Whoever eats at the beginning of the day, let him eat at the end of it." We said that it is obligatory for a student of knowledge in matters of disagreement to look at the evidence and adopt whichever is stronger in his view, and not to mind the disagreement of anyone as long as the evidence is with him. This is because we are commanded to follow the messengers, and on the Day of Judgment they will be called out and asked: "What did you follow of the messengers?" This brother, the questioner, said: Do those who say one must abstain have no basis in the authentic hadith where the Prophet (peace and blessings be upon him) ordered fasting on the Day of Ashura during the day, and the people abstained for the rest of the day? We say: You have no basis in this hadith, because the fasting of the Day of Ashura does not involve the removal of a barrier, but rather the renewal of the obligation. There is a difference between the removal of a barrier and the renewal of the obligation. The renewal of the obligation means that the ruling was not established before the existence of its cause. As for the removal of a barrier, it means that the ruling is established despite the barrier, were it not for this barrier. As long as this barrier exists along with the causes of the ruling, it means that the act cannot be valid with its presence. The parallel to this issue raised by the questioner is if a person becomes a Muslim during the day; for this person who became a Muslim, the obligation is renewed for him. The parallel is also if a boy reaches puberty during the day while his fast is invalid; for him, the obligation is renewed. So we say to the one who became a Muslim during the day: It is obligatory for you to abstain, but it is not obligatory for you to make up the fast. And we say to the boy who reaches puberty during the day: It is obligatory for you to abstain, but it is not obligatory for you to make up the fast. This is unlike the menstruating woman who becomes pure, for by the consensus of the scholars, it is obligatory for her to make up the fast. If a menstruating woman becomes pure during the day, the scholars agreed that even if she abstains for the rest of the day, this abstention does not benefit her, and it does not count as a fast, and she must make it up. For this reason, the difference is established between the renewal of the obligation and the removal of the barrier. The issue of the menstruating woman who becomes pure falls under the category of the removal of a barrier. The issue of the boy who reaches puberty, or what the questioner mentioned regarding the obligation of fasting on the Day of Ashura before Ramadan was made obligatory, falls under the category of the renewal of the obligation. And Allah grants success.