Nasai

216. Commentary:
➊ Menstrual blood is, in the beginning, more inclined towards blackness. Gradually, its color becomes lighter. In the end, it becomes red.
➋ A woman experiencing istihada (non-menstrual vaginal bleeding) will perform a new ablution (wudu) for every prayer. However, in “apparent combining” (jam‘ suri) and “actual combining” (jam‘ haqiqi), she may perform two prayers with one ritual bath (ghusl) and one ablution (wudu). The ruling of performing ablution for every prayer applies in the case when both prayers are performed at their earliest time. «والله أعلم»
The ruling of performing ablution for every prayer is because, in reality, due to the continuous flow of blood, her ablution does not remain valid, but the Shari‘ah, due to necessity, has made it obligatory for her to be in a state of ablution for the performance of prayer. After the performance of the prayer, since the necessity no longer remains, the original ruling returns, i.e., the absence of purity.
➌ Every person whose ablution does not remain valid, for example: if drops of urine keep coming out all the time, or wind keeps passing, etc., then the ruling for him is the same—that he should perform one prayer with one ablution, then perform a new ablution.

201. Commentary:
➊ "Hayd" (menstruation) is the blood that comes from the womb of every young woman regularly for a few days each month. It is a sign of a woman's health. The cessation or irregularity of this blood indicates that the woman is ill. When this blood is present, intercourse, prayer, and fasting are prohibited. When menstruation ends, that is, when this blood stops, ritual bath (ghusl) becomes obligatory. After performing the ritual bath, all these acts become permissible.
➋ "Istihada" refers to the blood that comes from the womb outside of those specified days; since it is an illness, the aforementioned acts remain permissible during it, and ritual bath (ghusl) is not obligatory because of it.
➌ The meaning of «عِرْقٌ» is "vein," which is near the womb, and from which this blood comes.

212. Commentary:
Imam al-Nasa’i rahimahullah’s intent is that this hadith was not heard by ‘Urwah directly from Fatimah bint Abi Hubaysh radi Allahu anha, as is apparent from the narration of Mundhir, but rather he actually heard this hadith from ‘A’ishah radi Allahu anha, as is understood from the upcoming hadith: [213]. Thus, the narration of Mundhir is disconnected (munqati‘). Furthermore, our esteemed researcher has declared Mundhir to be of unknown status (majhul al-hal), therefore the aforementioned narration is weak in terms of its chain of transmission. However, in meaning it is correct, because the next authentic narration conveys the same meaning. Also, Shaykh al-Albani rahimahullah has declared this hadith to be authentic; see: [صحيح سنن النسائي، للألباني، رقم : 221]

358. Commentary: The narration of Hisham bin Urwah comes after this. There are two differences between these two narrations: Firstly, in the narration of Hisham bin Urwah, it is not explicitly stated that Fatimah bint Abi Hubaysh radi Allahu anha narrated this directly to Urwah. Secondly, the words «ما بين القرء الي القرء» are not mentioned in it.

362. Commentary: There is some difference in the chain of narration between the two reports. In the narration from the Book, ‘Urwah relates directly from Fatimah bint Abi Hubaysh radi Allahu anha, whereas in the narration from Hafs, there is the intermediary of ‘Aishah radi Allahu anha. ‘Urwah heard the narration from both of them—from Fatimah as well as from ‘Aishah radi Allahu anha—because it is established that he met both of them. Some hadith scholars have considered this to be an error on the part of Ibn Abi ‘Adi and have declared the first narration to be disconnected (munqati‘), but the first view is correct. And Allah knows best. For further details, see Hadith: 216 and its benefits and issues.

280. Commentary:
It is understood that if the days and dates are already known and determined, then those very days should be counted as the days of menstruation (hayd). And if they are not known, then estimation should be made based on the color of the blood.

Commentary:
According to our researcher, this narration is weak in its chain of transmission, whereas its text and meaning are correct, as the same issue is mentioned in the following narration.
Most likely for this reason, other researchers have declared it to be authentic.

The word "quroo’" (قُرْؤُ) in linguistic terms refers both to the state of purity (tuhr) and to menstruation (hayd), but wherever it has been used in the Qur’an and Hadith, it has been used in the meaning of menstruation (hayd). This is the established and researched position. This hadith has already been discussed in the Book of Purification (Kitab al-Taharah).