Sayyiduna Ali (may Allah be pleased with him) said: When a woman becomes pure from menstruation, then after attaining purity she sees something that causes her doubt, then this is the movement of Satan in the womb. So when she sees something like a spot of blood, or a stain like that of nosebleed, or something like the washing of flesh, she should perform ablution for prayer and offer the prayer. But if she sees fresh blood in which there is no doubt, then she should leave the prayer (i.e., consider it menstrual blood). Imam Darimi (may Allah have mercy on him) said: I heard Yazid bin Harun say: If a woman's period of menstruation is seven days and she sees the whiteness of purity, then she gets married, and then within ten days from the seven-day period she sees blood, then her marriage is valid and correct. And if she becomes pure in less than seven days and gets married, then blood comes, her marriage is not valid and correct; that is menstrual blood. Imam Darimi (may Allah have mercy on him) was asked: Do you also say this? He replied: Yes.