Purity: Precaution for Acts Before Prayer Time
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 427:
If a woman with excessive or medium istiḥāḍah wants to recite a verse with an obligatory sajdah before the time for prayers, or if she wants to go to a mosque, then based on recommended precaution, she should perform ghusl. The same applies if her husband wants to have sexual intercourse with her.
-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)