Purity: Intermittent Bleeding Within Ten Days
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 442:
If a woman experiences bleeding for three consecutive days and then her bleeding stops, in the event that she experiences bleeding again and the days on which she experiences bleeding plus the days on which her bleeding stops in between altogether do not exceed ten, then the blood on all the days that she experienced bleeding is ḥayḍ. However, the obligatory precaution is that on the days that her bleeding stops in between, she must do the things that are obligatory for a non-ḥāʾiḍ and refrain from doing the things that are unlawful for a ḥāʾiḍ.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)