It was narrated from 'Aishah that a woman who suffered from Istihadah at the time of the Messenger of Allah ﷺ was told that it was a stubborn vein (i.e., one that would not stop bleeding). She was told to delay Zuhr and bring 'Asr forward, and to perform one Ghusl for both, and to delay Maghrib and bring 'Isha' forward, and to perform one Ghusl for both, and she would perform one Ghusl for Subh.  

أَنَّ امْرَأَةً مُسْتَحَاضَةً عَلَى عَهْدِ النَّبِيِّ ﷺ قِيلَ لَهَا إِنَّهُ عِرْقٌ عَانِدٌ وَأُمِرَتْ أَنْ تُؤَخِّرَ الظُّهْرَ وَتُعَجِّلَ الْعَصْرَ وَتَغْتَسِلَ لَهُمَا غُسْلاً وَاحِدًا وَتُؤَخِّرَ الْمَغْرِبَ وَتُعَجِّلَ الْعِشَاءَ وَتَغْتَسِلَ لَهُمَا غُسْلاً وَاحِدًا وَتَغْتَسِلَ لِصَلاَةِ الصُّبْحِ غُسْلاً وَاحِدًا  

"I said to the Prophet ﷺ that I was suffering from Istihadah. He said: 'Do not pray during the days of your period, then perform Ghusl and delay Zuhr and bring Maghrib and bring 'Isha' forward and pray them together, and perform Ghusl for Fajr."  

قُلْتُ لِلنَّبِيِّ ﷺ إِنَّهَا مُسْتَحَاضَةٌ فَقَالَ تَجْلِسُ أَيَّامَ أَقْرَائِهَا ثُمَّ تَغْتَسِلُ وَتُؤَخِّرُ الظُّهْرَ وَتُعَجِّلُ الْعَصْرَ وَتَغْتَسِلُ وَتُصَلِّي وَتُؤَخِّرُ الْمَغْرِبَ وَتُعَجِّلُ الْعِشَاءَ وَتَغْتَسِلُ وَتُصَلِّيهِمَا جَمِيعًا وَتَغْتَسِلُ لِلْفَجْرِ