It was narrated from 'Adiyy bin Thabit, from his father, from his grandfather, that:
The Prophet said: "The woman who experiences irregular non-menstrual bleeding should leave prayer during the days of her period, then she should take a bath, and perform ablution for each prayer, and she should fast and perform the prayer." (RU)
English reference (RU): Vol. 1, Book 1, Hadith 625 (RU)
Arabic reference (RU): Book 1, Hadith 668 (RU)