The ruling on the fast of one who has not confirmed her purity

The questioner : Another questioner says: A woman began fasting from the night, but she did not perform the full ritual bath until the time of the midday prayer. This is because she said she wanted to make sure she was pure, as she feared that impurity might come out of her. In the late morning, she saw the white discharge. What is the ruling on her fast?

The Shaykh : Her fast is not valid, because she fasted without making sure she was pure. The default is that menstruation remains until one is certain of purity. Likewise, whatever exists, the default is that it remains in its state of existence until certainty is established regarding the removal of that existence. This is based on the saying of the Prophet (peace and blessings be upon him) So we say to this woman who was not certain that she had become pure: Wait until you are certain of your purity. If she became pure during the day, she may continue fasting if she wishes, or she may not continue if she wishes. That is, if she remains in the state of having broken her fast, there is no harm. The stronger position among the opinions of the scholars is that if a woman becomes pure from menstruation during the day, or if a traveler arrives while he is not fasting and arrives in his hometown during the day, the stronger position among the scholars' opinions is that they are not required to continue fasting. This is one of the two narrations from Imam Ahmad (may Allah have mercy on him).
And there is no evidence for the obligation of continuing to fast without benefit, because if we say "continue fasting and you must make it up," it becomes mere torment for this man without any legal benefit.