"Fatimah bint Abi Hubaish came to the Prophet: 'O Messenger of Allah! I am a woman who bleeds continuously and never becomes pure. Should I give up prayer?' he said: 'No, that is just a vein and is not menstruation. Do not perform prayer during the days of your period, then take a bath, and perform ablution for each prayer, even if drops of blood fall on the mat.'" (Using translation from Ibn Mājah 624)
عَنْ عَائِشَةَ جَاءَتْ فَاطِمَةُ بِنْتُ أَبِي حُبَيْشٍ إِلَى النَّبِيِّ ﷺ فَقَالَتْ يَا رَسُولَ اللهِ إِنِّي امْرَأَةٌ أُسْتَحَاضُ فَلَا أَطْهُرُ أَفَأَدَعُ الصَّلَاةَ قَالَ لَا اجْتَنِبِي الصَّلَاةَ أَيَّامَ مَحِيضِكِ ثُمَّ اغْتَسِلِي وَتَوَضَّئِي لِكُلِّ صَلَاةٍ ثُمَّ صَلِّي وَإِنْ قَطَرَ الدَّمُ عَلَى الْحَصِيرِ وَقَدْ قَالَ وَكِيعٌ اجْلِسِي أَيَّامَ أَقْرَائِكِ ثُمَّ اغْتَسِلِي