Uncertainty Concerning When Menstruation Began and Its Effect on Fasting and Salah

Firstly:

Your fasting for this day is valid because you did not see the blood nor feel its discharge before Maghrib, and the principle is that if there is doubt about the timing of the blood discharge, whether it was before or after Maghrib, it is is attributed to the nearest time, and this is one of the principles of Jurisprudence. The nearest time here is after Maghrib.

The meaning of the principle is: "When there is a difference in the timing of an event's occurrence, and there is no evidence to determine it – then this event is attributed to the closest time to the current situation; because that is certain, and the further time is doubtful. However, if its attribution to the further time is established, then it must be acted upon." End quote from "Encyclopedia of Jurisprudential Principles" by Dr. Muhammad Sidqi Al-Borno (12/316).

As-Suyuti (may Allah have mercy on him) said in his book "Al-Ashbah wan-Nadha'ir" page 59: "Principle: The origin of every event is to estimate it by the nearest time. Among its branches: If he sees semen on his garment and does not remember having a wet dream, the correct opinion is that he must perform Ghusl. Ash-Shafi`i said in Al-Umm: 'And he must repeat every Salah he has performed since the last time he slept.'" End quote.

Secondly:

As for the Maghrib prayer, if you think it most likely that the blood was discharged during it due to the light pain—as you mentioned—and because you saw the blood fresh after the prayer, and the like, which indicates a most likely opinion, then the prayer is not valid, and you must repeat it once you become pure.

If there is no feeling of likelihood, but rather doubt, then the prayer is valid; because of what we have previously mentioned that the event is attributed to the nearest time, and it is judged that the blood was discharged after the prayer.

Sheikh Muhammad ibn Muhammad Al-Mukhtar Ash-Shanqiti (may Allah preserve him) was asked about a woman who saw some menstrual blood after the Maghrib prayer and did not know whether it was discharged before sunset or after; what is the ruling regarding her prayer and fasting?

He replied: "If she saw the blood and thinks it most likely that it was discharged before sunset, then there is no doubt that the fast of that day is void and she must make it up.

But if she thinks it most likely that the blood is fresh and that it was discharged after Maghrib, then there is no doubt about the validity of her fast, and the Maghrib prayer is obligatory when she becomes pure; for she must make it up and perform it.

But if she is hesitant and doubtful, then the principle among the scholars (may Allah have mercy on them) says: (It is attributed to the nearest event), so the original ruling is the validity of the fast until evidence indicates its invalidity, and the original ruling is that she fasted a complete day, and she is free of liability until we ascertain the existence of this factor, so her fast is judged to be valid.

As for the blood, it has no effect on that day, and the issue remains the opposite, because if you say: her fast is valid, she is obliged to make up Maghrib, and if you say: her fast is not valid, there is no making up of Maghrib, for if she is exempted from fasting, she is obliged to make up Maghrib; because the entry of the time renders the menstruating woman liable, and it is not considered at the end of the time as the Hanafi Jurists and some of the companions of Imam Ahmad say." End quote from "Explanation of Zad Al-Mustaqni` by Sheikh Ash-Shanqiti."

For more benefit, please see the answer to question number: (191684 ).

And Allah knows best.