How can one differentiate between menstrual blood and istiḥāḍah blood, and what is the ruling if the blood has an odor during the period of istiḥāḍah, and is there a requirement for qaḍāʾ (making up) or kaffārah (expiation) for one who prayed or engaged in sexual intercourse, believing the discharged blood to be istiḥāḍah blood because she is breastfeeding and does not recall the number of days?

Menstrual blood is black, thick, and foul-smelling, and its characteristics distinguish it from other types of blood, especially if its flow exceeds fifteen days. If it does not exceed this period, then all blood is considered menses, even if its characteristics differ. If you prayed during your menstruation out of ignorance, there is no sin upon you, for the Prophet, peace and blessings be upon him, said: "Indeed, Allah has pardoned for my Ummah their mistakes, their forgetfulness, and what they are forced to do." There is no sin upon you or your husband for engaging in intercourse out of ignorance. However, if intercourse is deliberately performed during menstruation, the person is sinful and is required to offer expiation by donating a dinar or half a dinar.