Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
darimi:835Muḥammad b. Yūsuf > Sufyān > Sumay > Saʾalt Saʿīd b. al-Musayyib > al-Mustaḥāḍah

[Machine] "She sits and recites her days, and she washes herself from noon till noon, and she seeks forgiveness in a gown and her husband comes to her, and she fasts." So I said, "Who is this?" He took pebbles."  

الدارمي:٨٣٥أَخْبَرَنَا مُحَمَّدُ بْنُ يُوسُفَ حَدَّثَنَا سُفْيَانُ عَنْ سُمَيٍّ قَالَ سَأَلْتُ سَعِيدَ بْنَ الْمُسَيِّبِ عَنِ الْمُسْتَحَاضَةِ فَقَالَ

«تَجْلِسُ أَيَّامَ أَقْرَائِهَا وَتَغْتَسِلُ مِنَ الظُّهْرِ إِلَى الظُّهْرِ وَتَسْتَذْفِرُ بِثَوْبٍ وَيَأْتِيهَا زَوْجُهَا وَتَصُومُ» فَقُلْتُ عَمَّنْ هَذَا؟ «فَأَخَذَ الْحَصَا»