Hadith: After becoming pure, we did not consider turbid and yellowish discharges to be of any significance

عن أم عطية، نُسيبة بنت الحارث الأنصارية رضي الله عنها قالت: «كنا لا نعد الْكُدْرَة وَالصُّفْرَة بعد الطهر شيئًا».
[صحيح] - [رواه أبو داود بهذا اللفظ، ورواه البخاري بدون زيادة (بعد الطهر)]

Umm ‘Atiyyah Nusaybah bint al-Hārith al-Ansāriah (may Allah be pleased with her) reported: After becoming pure (from menstruation), we did not consider turbid and yellowish discharges to be of any significance.
Sahih/Authentic. - [Al-Bukhari with a similar wording]

Explanation

Umm ‘Atiyyah (may Allah be pleased with her) reported one of the tacit approvals from the Sunnah regarding the blood that women discharge from their wombs. She said that after the monthly menses is over, they did not consider as menstrual blood any turbid discharge, i.e. what resembles dirty turbid water, and any yellowish discharge, which is similar to pus in color. The pronoun 'we' used in her statement, according to the scholars' most prominent opinion, takes the ruling of being attributed to the Prophet (may Allah's peace and blessings be upon him) because she meant to say: we used to do so during the lifetime of the Prophet (may Allah's peace and blessings be upon him) and with his knowledge, so this entails his approval. It is a proof that what is not thick dark blood is not considered menses after the end of menses. The end of menses has two signs: 1. "Qassah": a discharge that resembles a white thread and comes out of the womb after cessation of menstrual blood. 2. "Jufūf": dryness such that when something is inserted in the womb it comes out dry. What is understood from her words 'after becoming pure' is that the yellowish and turbid discharges during the days of the menses are considered part of the menses.