حَدَّثَنَا الْقَعْنَبِيُّ، حَدَّثَنَا عَبْدُ الْعَزِيزِ، - يَعْنِي ابْنَ مُحَمَّدٍ - عَنْ مُحَمَّدِ بْنِ عُثْمَانَ، أَنَّهُ سَأَلَ الْقَاسِمَ بْنَ مُحَمَّدٍ عَنِ الْمُسْتَحَاضَةِ، فَقَالَ تَدَعُ الصَّلاَةَ أَيَّامَ أَقْرَائِهَا ثُمَّ تَغْتَسِلُ فَتُصَلِّي ثُمَّ تَغْتَسِلُ فِي الأَيَّامِ ‏.‏

Muhammad b. 'Uthman asked al-Qasim b. Muhammad about the woman who has a prolonged flow of blood. He replied: She should abandon prayer during her menstrual period, then wash and pray ; then she should wash during her menstrual period. Translation Not Available

Book Ref: Sunan Abi Dawud Book 1 Hadith 303
Web Ref:  Sunan Abi Dawud Book 1 Hadith 303