Purity: Istiḥāḍah Discharge Before Prayer Time
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 395:
If the blood of istiḥāḍah is discharged before the time for prayers, in the event that a woman has not performed wuḍūʾ or ghusl [depending on her duty] for it, she must perform wuḍūʾ or ghusl at the time of prayers, even if she is not mustaḥāḍah at that moment.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)