[Machine] Abi Hubayshah was experiencing istihaadah (irregular bleeding) so she asked Umm Salamah and the Messenger of Allah ﷺ. The Prophet ﷺ said, "It is not menstruation; rather, it is only a vein. He commanded her to refrain from praying during the days of her regular period and the days of her irregular bleeding. Then she should perform ghusl (ritual bath) and pray. If the bleeding overwhelms her, she should consider it as her regular period." This is what I found, and the correct opinion is that it could be either the days of her regular period or the days of her istihaadah, with doubt. And similarly...  

أَبِي حُبَيْشٍ ؓ اسْتُحِيضَتْ فَسَأَلَتْ لَهَا أُمُّ سَلَمَةَ ؓ رَسُولَ اللهِ ﷺ فَقَالَ النَّبِيُّ ﷺ لَيْسَتْ بِالْحَيْضَةِ إِنَّمَا هُوَ عِرْقٌ فَأَمَرَهَا أَنْ تَدَعَ الصَّلَاةَ أَيَّامَ أَقْرَائِهَا وَأَيَّامَ حَيْضِهَا ثُمَّ تَغْتَسِلَ وَتُصَلِّيَ فَإِنْ غَلَبَهَا الدَّمُ اسْتَدْفَرَتْ كَذَا وَجَدْتُ وَالصَّوَابُ أَيَّامَ أَقْرَائِهَا أَوْ أَيَّامَ حَيْضِهَا بِالشَّكِّ وَكَذَلِكَ