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." (ES)
English reference (ES): Vol. 1, Book 1, Hadith 625 (ES)
Arabic reference (ES): Book 1, Hadith 668 (ES)