Purity: Doubt About Wudu During Prayers

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 304:

If a person doubts during prayers whether or not he had performed wuḍūʾ, then based on obligatory precaution, he must perform wuḍūʾ and perform the prayer again.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)