What is the minimum and maximum duration of post-natal bleeding and menstruation?

The questioner : What is the minimum and maximum duration of post-natal bleeding, O Shaykh?

The Shaykh : There is no minimum or maximum limit for post-natal bleeding or menstruation; rather, the matter varies according to the differences among women and their different customs. What men should know before women do—because men are the protectors and maintainers of women—is that menstrual blood has a sign, as he (peace and blessings be upon him) said in the authentic hadith: , and in another wording: , meaning: it has a smell. The other wording is: meaning: the distinctiveness of menstrual blood among women from other bloods, such as blood from wounds or blood from irregular non-menstrual bleeding, is known. So when a woman sees this black blood that is known to them, she becomes menstruating. When does she become pure? We said: Menstruation does not have a fixed duration, whether short or long. So when does she become pure? She becomes pure when she sees what is called in the language of the Shari'ah "the white flag," and in common language it is "purity." The women in the era of the Salaf, in the era of the Companions, would come to A'ishah, first because she was the Mother of the Believers, and second because she was the most knowledgeable of the women regarding the rulings of Islam in general and the rulings concerning women in particular. She may have been more knowledgeable in some of these matters than many of the men among the Companions of the Messenger (peace and blessings be upon him). So when a woman would doubt her purity—whether she had entered the stage of purity after menstruation or not—A'ishah would order the woman to pack herself with white cotton and tell her: "If you do not see any trace, even if it is yellow, on this cotton, but only white, then this is 'purity' in common language, and it is 'the white flag' in the language of A'ishah." If she sees this purity, she has become pure, whether it is an hour of the day, a day, a night, or more or less; it is not important.
This is the ruling on menstruation, and the ruling on post-natal bleeding is the same. If a woman gives birth, she does not have a fixed duration. However, post-natal bleeding differs from menstruation in terms of quantity. If a woman in post-natal bleeding stops bleeding and sees the white flag as we mentioned earlier, she has become pure, no matter how short the duration was. But if the blood continues with her beyond forty days, then the forty days are the days of post-natal bleeding during which she does not pray or fast. Anything after the forty days is irregular non-menstrual bleeding, so she fasts and prays and does everything that Allah (Mighty and Majestic) has made permissible for her.
The Shaykh : Yes, do you have anything else?

The questioner : The matter of the forty days, my master, why forty? I mean, why did we link the number forty to the matter? Why wasn't it thirty or fifty, for example?

The Shaykh : This is a good question, because that is how the Sunnah is. Some women—perhaps it was Umm Salama—said: "The woman in post-natal bleeding in the time of the Prophet (peace and blessings be upon him) would stay for forty days." This is where the specification of forty days came from. Perhaps you have received the answer to your question?

The questioner : May Allah reward you with good.

The Shaykh : And beware of that.
Other than that?