If a menstruating woman's period is delayed, what should she do?

The Shaykh : It is delayed, for example, if her custom is for menstruation to come at the beginning of the month, but it is delayed. According to what the author followed, if it comes at the end of the month, she does not sit (i.e., she does not observe the waiting period for menstruation). Even if it is the blood of menstruation that she recognizes by its smell, thickness, and blackness, she does not sit until it recurs three times. Then she prays and fasts. If it recurs three times, she makes up the fast, meaning she makes up what is obligatory for a menstruating woman to make up. Do you understand now? The stronger opinion in this issue is like the first one: if her custom is delayed and it comes at the end of the month, it is obligatory for her to sit (observe the waiting period), because, as we mentioned before, it is known by the description of Allah, who described it as permitted.