أَخْبَرَنَا مُحَمَّدُ بْنُ عِيسَى، حَدَّثَنَا هُشَيْمٌ، حَدَّثَنَا يُونُسُ، عَنْ الْحَسَنِ، قَالَ: "تُمْسِكُ الْمَرْأَةُ عَنْ الصَّلَاةِ فِي حَيْضِهَا سَبْعًا، فَإِنْ طَهُرَتْ، فَذَاكَ، وَإِلَّا أَمْسَكَتْ مَا بَيْنَهَا وَبَيْنَ الْعَشْرَةَ، فَإِنْ طَهُرَتْ، فَذَاكَ، وَإِلَّا اغْتَسَلَتْ وَصَلَّتْ، وَهِيَ مُسْتَحَاضَةٌ".
It is narrated from Yunus (bin Ubaid) that Imam Hasan al-Basri, may Allah have mercy on him, said: A woman will refrain from prayer during her menstruation for seven days, then if she attains purity, that is fine; otherwise, she will refrain from prayer for up to ten days from the start of her menstruation. If she becomes pure at ten days, that is fine; otherwise, she should perform ghusl and pray, and she will be considered mustahadah (one experiencing non-menstrual bleeding).