[Machine] Anas ibn Malik said that the menstrual period lasts for five, six, seven, eight, or eighteen days. After that, she should perform ghusl (a full-body wash), fast, and pray. This is a hadith narrated by Jild ibn Ayyub, and it has been disputed.
قَالَ أَنَسُ بْنُ مَالِكٍ قُرْءُ الْحَائِضِ خَمْسٌ سِتٌّ سَبْعٌ ثَمَانٍ عَشْرَةٌ ثُمَّ تَغْتَسِلُ وَتَصُومُ وَتُصَلِّي فَهَذَا حَدِيثٌ يُعْرَفُ بِالْجِلْدِ بْنِ أَيُّوبَ وَقَدْ أُنْكِرَ ذَلِكَ عَلَيْهِ