Qasim Ja'far ibn Muhammad, from Muhammad ibn Ya’qub, from Ali ibn Ibrahim, from his father, from Isma'il ibn Marrar, from Yunus, from one of his companions, from Abu Abdullah عليه السلام, who said:
Imam عليه السلام said: "The minimum duration of purity is ten days. This is because when a woman first starts menstruating, she might have a heavy flow lasting ten days. As she grows older, it decreases until it reaches three days. When it reaches three days, her menstruation ceases and does not go below three days. If a woman sees blood during her days of menstruation, she must stop praying. If the blood continues for three days, she is considered menstruating. However, if the blood ceases after one or two days, she must perform ghusl (ritual purification) and resume her prayers. She should observe herself from the day she first saw the blood until ten days. If she sees more blood within those ten days, even for one or two days, making up a total of three days, then the blood seen at the beginning and the subsequent blood are part of the same menstruation. However, if ten days pass without seeing further blood, the one or two days of bleeding she initially experienced were not menstruation but rather due to some condition, such as an internal sore or another cause. In this case, she must make up the prayers she missed during those days because they were not menstruation. If she experiences three days of bleeding, this constitutes menstruation, which is the minimum duration. She does not have to make up her prayers, and the minimum interval of purity between two periods is ten days. If a woman menstruates for five days and the bleeding ceases, she performs ghusl and resumes her prayers. If she sees blood again within ten days of her initial cessation, it is part of the same menstruation, and she must refrain from praying. If she sees blood again on the tenth day and it continues, she considers the first instance of bleeding and the second as part of a single twelve-day period. Afterward, she is deemed mustahadha (experiencing irregular bleeding) and follows the relevant rulings for mustahadha.” Imam عليه السلام also said: “Whenever a woman sees yellowish or reddish discharge during her menstruation days, it is considered menstruation. Anything she sees after her menstruation days is not menstruation.'"
