She went to the Messenger of Allah and complained to him about bleeding. The Messenger of Allah said: "Rather that is a vein, so look and see when your period comes, then do not perform the prayer. When the period is over, then purify yourself and perform the prayer between one period to the next." (Using translation from Ibn Mājah 620)  

أَنَّهَا أَتَتِ النَّبِيَّ ﷺ فَشَكَتْ إِلَيْهِ الدَّمَ فَقَالَ لَهَا رَسُولُ اللهِ ﷺ إِنَّمَا ذَلِكَ عِرْقٌ فَانْظُرِي فَإِذَا أَتَاكِ قُرْؤُكِ فَلَا تُصَلِّي فَإِذَا مَرَّ الْقُرْءُ فَتَطَهَّرِي ثُمَّ صَلِّي مَا بَيْنَ الْقُرْءِ إِلَى الْقُرْءِ