Urwah ibn az-Zubayr said that Fatimah daughter of AbuHubaysh narrated to him that she asked the Messenger of Allah ﷺ and complained to him about the flowing of (her) blood. The Messenger of Allah ﷺ said to her: That is only (due to) a vein: look, when your menstruation comes, do not pray; and when your menstruation ends, wash yourself and then offer prayer during the period from one menstruation to another. (Using translation from Abū Dāʾūd 280)  

أَنَّهَا أَتَتْ رَسُولَ اللهِ ﷺ فَشَكَتْ إِلَيْهِ الدَّمَ فَقَالَ لَهَا رَسُولُ اللهِ ﷺ «إِنَّمَا ذَلِكَ عِرْقٌ فَانْظُرِي إِذَا أَتَى قُرْؤُكِ فَلَا تُصَلِّي فَإِذَا مَرَّ قُرْؤُكِ فَتَطَهَّرِي ثُمَّ صَلِّي مَا بَيْنَ الْقُرْءِ إِلَى الْقُرْءِ»