It was narrated that Umm Salamah said:"A woman asked the Prophet: 'I bleed continuously and I do not become pure. Should I give up the prayer?' He said: 'No, but leave off praying for the number of days and nights that used to menstruate.'" (One of the narrators) Abu Bakr (Ibn Abu Shaibah) said in this Hadith: "Estimate the number of days in the month, then take a bath and cover your private part with a cloth and perform prayer

English translation · Sunan Ibn Majah